Develop Reference

Are Hybrid Mobile apps generally considered inferior to Native apps by developers in the tech industry?

For a college project, my group was planning on making a cloud messaging app for Android. Initially we began development by studying and using Ionic Framework and Phonegap to create a Hybrid app.
Based on what we had read and learnt so far what we understood was with Hybrid app development allows us to code with web technologies(HTML, CSS Javascript) which we were quite familiar with in far less time than building a Native app. It also had the plus of running on multiple platforms with very minor tweaking.
But as we moved forward we got some strange feedback from many of our colleagues and people in the field which all pointed to one thing;
a general distrust and doubtfulness about Hybrid apps.
Eventually we decided to go for a Native app due to this feedback among other reasons but it always bothered us why people felt that way.

Yes, the general sentiment is that Hybrid apps are inferior to Native apps. While this can be frustrating for developers more familiar with web technologies, it does come for good reason:
Inability to interact with native components: Although plugins such as cordova-plugin-statusbar exist, there are limitations interacting with and manipulating native components using web technologies. One great (and frustrating) issue I have personally run into is the inability to have an input at the top of they keyboard as the keyboard animates in. This sounds like a nonissue until you look at an app where this is an essential feature such as in a chat app like Slack.
300ms delay: Although modern browsers are beginning to phase this out, the fraction of a second delay present on Hybrid apps makes the app feel slow and non-native. This issue is becoming less of a factor as more users adopt workarounds such as FastClick.js and some frameworks such as Ionic eliminate it by default.
The haters are right (sort of): While Hybrid app development has come a long way, there are still minor glitches and laggy functions that are just not present in a Native app. Screen transitions, app switching, and battery life are still common areas for bugs to appear and likely will be for some time, even if they are starting to become less and less noticeable.
There are some great Native solutions: With newer languages such as Apple's Swift it is becoming easier to code in a Native language. That being said, tools such as React Native fall into a gray area between Native and Hybrid by allowing developers to code in friendly technologies such as JavaScript but compile into native code.
The moral of the story is that it really depends what is important to your specific use case. Hybrid apps have become a viable option and are no longer an embarrassing side show. Conversely, there are still minor aspects of interacting with the Native UX that are not yet possible except with a Native app.
Overall, I recommend mapping out your project and determining if your app needs any of the benefits of a Native app. With tools such as the Ionic View app it is easy to put together a basic mockup of your app and test on a real device whether or not a Hybrid app will work for you.

Building a hybrid app, where to start?

I know it's kind of an 'open' question to ask but I simply don't know where to start. Let me first tell you a bit of my experience/background so you know the level I'm at:
Build cd-roms with Lingo back in the days
Started web/front end development in the HTML3.2 era and kinda left off when XHTML was hot
Worked with Javascript 1.2 up till around 1.6 and later started working with Jquery
Actionscript up to 2.0, building websites and games
Did quite a bit of PHP/mySQL development. Build custom CMS' and later Drupal module development
All this was during internships or as a freelancer, everthing self thought by the help of books and such
So now I'm stuck with this idea to build myself an app. I've decided it should be an hybrid app as my target audience is very small but 60% is iOS and I don't want to leave out Android. Also I've been getting familiar with HTML5/CSS3 and started working on components for my app.
The basic concept for the app is that it's a layer on top of Google functionality: profile, calendar, circles and hangouts. Users will (eventually I hope) be able to create events for other users to rsvp to, they will be able to add eachother as buddies and chat about the events. A small step functionality wise but a huge step for me :)
I'm thinking of using the Crosswalk project for the Android version to counter the biggest issues around hybrid app development.
I've been reading up for the last months in preparation and the more I read the less I seem to know. Here's the stuff I think I should know more about;
Node.js
Gulp.js
Dev environment to work in (I once worked in Homesite, later Dreamweaver - don't laugh)
Packaging tools, etc etc.
Crosswalk project
Now I am not looking for some drag and drop software package to build an app in 3 days. I don't want to take the easy route per se, I don't mind a bit of a learning curve. I work on a Win8 machine, I know this isn't optimal but I can't change this.
Now where should I start? I was thinking NPM myself but you guys might think otherwise. Any good books on the stuff you think I need to learn to get me going?
Thanx for the advice!

I can share my experience with Cordova.
I work like full-stack developer and i'm quite expert to build responsive website, so the natural step to approach mobile dev was try Cordova.
First You can start to build HTML document totally responsive and try as webpage on your target devices.
A cool stuff, targeting mobile devices, is that You can use new CSS3 directive, without worry for compatibility with old browser.
First I installed Cordova following this tutorial.
https://ccoenraets.github.io/cordova-tutorial/create-cordova-project.html
Opening the folder /www on your project you can edit your app like a website, and you can also debug with the browser like a normal site.
To enhance the feature you will find a lot of plugins ready on github to extends the native functionality at the Cordova/phonegap project.
I suggest you also to build using onsen http://onsen.io/ a framework that let you use mobile UI easily.
Last tip that i can give you, if you target Android is try your apps on virtual machine, i use Genymotion https://www.genymotion.com/ that is much more fast then SD<
Good luck with your first app!

As you can imagine, there are a lot of framework where you can start.
Looking on your skills, maybe is better to use JS/HTML/css stack, but in this case, you will create an hybrid app in a webview.
In my opinion, webview applications quality it's only acceptable, but because of his productivity, in some cases could be the best decision.
Another good alternative is react-native. This framework allows to create a native application using javascript. React has his own markup language, is very similar to html. JS code is executed on native device using an embedder javascript engine, instead of webview, so, performances and experience can be compared to native applications.
And, at the end, my alternative, a framework I've made to write native UI and share business logic for each platforms. You can take a look on aj-framework https://github.com/bfortunato/aj-framework

Developing in Android Studio versus Framework (e.g PhoneGap)

I wanted to get a more experienced opinion on something I recently found out. A couple of months ago I set a goal to build myself a mobile app, and the first thing I did was go to developer.android.com and begin reading documentation on how to go about doing this.
I've invested a lot of time in understanding Android Studio and how to make simple apps (and I'm just now getting the hang of it all), but I just recently read about frameworks like PhoneGap(which let web devs who know HTML,CSS, and Javascript make apps too).
Before learning Android, I taught myself web dev through the Odin Project, which taught me a fair amount of HTML, CSS, and Javascript (little iffy on this language, but I'm sure it's something I could pick up easily since I already have a bit of experience).
I'm wondering what you guys feel are the limitations of using these frameworks and whether I should switch over to them, as opposed to continuing with Android since things are beginning to click for me.
Thanks!

I have developed apps for both Android and Phonegap. Phonegap takes advantage of your web development experience and lets you build mobile apps with ease. But it's not a replacement for Android API itself. A good phonegap application requires knowledge about web development and Android API.
However if your aim is to develop an android application, and you are comfortable with web development and Android, I would advice to take Android API.
Phonegap as wonderful as it is for web developers, and startups who can't afford to have dedicated resources for Android, iOS separately, has its limitations.
Performance : Phonegap app's performance is not at par with a native
android application.
Functionality : As one would expect you can't have all the functionality support a native android application has.
Look : You could easily tell apart a phonegap application from a native one. Given phonegap renders all the content in a webview, the look of native ui elements is lost

I think you will always need access to the native API to make good apps.
At least the navigation should be native, so that your app has the look and feel that the user expects, and so that stuff like the back button get correctly handled for you.
Even if there is some plugin that does that for you in a perfect way, I believe it's beneficial to know how Android works.
In the end, frameworks like PhoneGap add a layer inside your app rather than removing one, and it's always better to understand what goes on inside your app.
So the time that you've spent learning native Android won't be lost.
However, it makes sense to use HTML/JS if you want to share code between different platforms.
I think this article from Basecamp shows a very compelling example: https://signalvnoise.com/posts/3743-hybrid-sweet-spot-native-navigation-web-content.

Struggling between native and phonegap, simple app requirements

I'm going to make a native (meaning; not in the browser) mobile app. Since I'm a web-developer I'm struggling to decide whether or not I should try Phonegap or just build an native app in java or objective-c.
The app requirements are simple. GPS/wifi location, Facebook integration and I guess I'll need a database to handle some of the application specific Facebook-friend relations. Like the highscores in a game, for example - stuff like that.
I'm a web-developer, and don't know neither java or objective-c, yet. I've never used Phonegap before, so I don't know if it's capable of fulfilling my requirements.
So my question is as follows;
Can I use Phonegap for my app, or do I need to dive into a new language?

Related:
Larger version of this article can also be found HERE, to be transparent it is my personal blog.
Hybrid vs Native apps
Hybrid apps:
Pro:
Quicker development, especially if you're a a longtime web developer.
1 language can be used on every available platform. This, of course, requires a Phonegap wrapper. You don't need to learn Objective C, Java, or C# to do any development. You need only to understand the basics of the Phonegap implementation. You will need to play with above-mentioned languages a bit but you don't need to understand them.
Phonegap can offer some native capabilities like iOS native tab bar or Android native tab bar and so much more.
Lower budget costs and a huge community of supporters and developers.
A hybrid app offers many of the advantages of both approaches access to the most common device APIs, and broad device coverage while not requiring the specialized skills, bigger budgets and longer time to market that are more typical of fully native apps.
Cons:
You will piss blood after some time, literally and metaphorically.
Mobile phones (even today's tablets) are not fast enough to smoothly run a hybrid app, mobile JavaScript capabilities are bed at best. Android platform is a nightmare, page transitions don't work smoothly not to mention lacking CSS/CSS3 implementation. If you think native Android 2.X and 4.X have differences take a look a Android 2.X bad JavaScript / CSS implementation. iOS fares better but still has a lacking CSS3 implementation thou much better page transitions. To make this short native apps will always have a better user experience and general feeling.
You will spend much more time fixing the app then building it. Creating an app for each and every platform is a pain in the neck. Browsers on different platforms do not uniformly support all the latest HTML features and APIs, which can make developing and testing a challenge.
If you don't have a good designer, don't even try to build an app; looks are everything.
If you don't know what are you doing there's a good chance your app will not get permission for Apple app store. Even Google Play Store will ban your app if they discover a 3rd party Phonegap PayPal plugin.
Native apps:
Pro:
A native mobile app can produce the best user experience — fast and fluid, can give you the best access to device features, and can be discovered in the app stores.
Without a doubt, native apps have full access to the underlying mobile platform. Native apps are usually very fast and polished, making them great for high performance apps or games. This is more then enough.
Cons:
Bigger budget, you will need at least a person/s with Java and Objective C knowledge, even C# if you want a Windows mobile app. Yes you can learn it yourself but don't live under the illusion you will do so in a short time. If you have never done any development, choose Objective C (iOS is still a better platform). In other cases choose Java. Java has a syntax similar to other available languages, so it is easy to jump from C# to Java and vice-versa. Objective C is a world of it own. It has a rather uncommon syntax.
It might take you a longer period of time to develop all of them and time is money. This depends on the complexity of the apps.
In your case, if you have a good web development/design skills and/or have a good designer you should choose a hybrid app. Go native only if this app is going to be a complex one. Everything you want can be done with a hybrid app. And you will find a great and supporting community.
Hybrid apps
What I didn't previously mentioned you need to be specially careful here. Even if you are seasoned developer you will find a lot of problems you can't solve. Hybrid development should not be mistaken for a basic web development.
Every mobile platform has its own set of problems, not to mention that mobile phones behave differently depending on a device. If possible always create a app that works on a slower devices because native app will successfully work on almost any device.
There's one last thing, when creating hybrid apps, app development will take you about 30%-50% of your time, rest goes to specific platform debugging and learning. Believe me, even after several years of mobile development sometimes I am facing problems I can't solve alone or fast enough.
So be careful when choosing mobile framework, pick 2-3 and spend several days reading about them.
Links
Here are few links to help you decide:
PhoneGap + jQuery Mobile 1.4 tutorial - This is a step by step tutorial for PhoneGap and last version of jQuery Mobile
PhoneGap + jQuery Mobile 1.4 tutorial - MacOS version - This is a step by step tutorial for PhoneGap deployment on MacOS. jQuery Mobile part is covered in a previous article, no point in repeating things.
jQuery Mobile vs Sencha Touch - jQuery Mobile Sencha Touch comparison
jQuery Mobile vs Kendo UI - jQuery Mobile Kendo UI comparison
7 best known HTML5 mobile frameworks - Name tells everything
7 less known HTML5 mobile frameworks - Name tells everything

if your application does't have animation effects and simple i prefer to create in a web(Phonegap) cz at less amount of time we can launch in multiple types of mobile OS.
if your app contain more UI effects and animation then it is best to go with native..
even though you develop in webview(Phonegap) you need learn some basic steps in Android and iOS
How Phonegap performs in devices
Ios
The animations and view loading in ios webview is stranded and good, the animation effects can observer clearly
Android
We have to consider the device version and device company for android while running the html code, Some high config devices in android give more clear and efficient animation display, but some devices (mostly old version and some company devices) cant give good animation effects, rendering effect varies from device to device in android,

In my humble opinion with Phonegap you can just develope simple apps, nothing more. The documentation is not enough and like others have said you will spend much more time fixing bugs and finding plugins than building your app. I would make the effort to learn Android or iOS or whatever, look at it as an investment of your time. (Yes, my comment is a little biased).

Last I looked into it PhoneGap was all html,css, and javascript. So, you may feel right at home. PhoneGap can handle GPS location, see this article from PhoneGap's documentation. Whether or not you want to pick up Objective C would depend on how fast you pick up new languages as it is a bit of a departure from web development.

It totally depends on your needs
After publishing my first app several months (native Android, database driven, restful connecting app), I decided to rewrite my app by using phonegap (since I want to clone the app to iOS, so instead of doing it in ObjC, why not javascript ?)
When on Android, it costed me, a Java developer, 3 weeks to learn and code everything from scratch. Banging my head to the wall several times for how to make the ListAdapter sync with the Restful Service from my server, how to theme the app (quite hard in my opinion, especially when it comes to special effects like transparent, border,...), and also, how to structure your code base effectively (if you are familiar with Java, you will find that all the classes are very coupled to each others, since that is what most of the tutorials write about)
When on Phonegap, everything is done in 1 week. Css, html, with onsenui and angular make the GUI development just like about 1 st year student 's assignment and theming is just a piece of cake. I don't need to run it on the real device, just use browser during the development, change code and refresh are enough. Angular provides 2 way binding with the DOM, and this makes a huge awesomeness when collecting and showing data. For example:
<ul ng-each="for sentence in sentences" >
<li>{{ sentence.title }} </li>
</ul>
When the variable sentences is changed (retrieved from server), the DOM is automatically changed as well. However, javascript is only javascript. I found myself struggling many time when debugging the app, especially when doing the MapReduce functions with PouchDB (big mistake, have to go back to cordova-sqlite-plugin tonight) and most of the time, I have to read the log in order to figure out the problem (Chrome 's tools and Firebug cannot catch the breakpoint). Also, it is hard to restructure your app (javascript, again) so if you don't organise carefully your code base at the first sign, you might end up with a mess (and debugging is a real pain, again). PhoneGap is also Web based, so sometimes, you will hear that "because on this platform, it does not support that bla bla bla" (e.g, localStorage) and you have to stand for it if you cannot find any good plugin.
Conclusion Except for the limitation of the web-based storage, PhoneGap works quite well with the database driven, simple GUI app (and most of the database driven apps currently has a simple GUI anyway). If you gonna develop that kind of app, then stick with it

check out using ionic, backed by angular.js to offset some of the cons mentioned in the accepted answer. Tutorial for launching an employee directory app: http://coenraets.org/blog/2014/02/sample-mobile-application-with-ionic-and-angularjs/

#Gajotres wrote a great response, but hybrid app performance has come a long way since 2012. I answered a related question that covers the difference between hybrid and native app development in 2017.
The moral of the story is that hybrid app development has improved tremendously in the past few years, but it still cannot match native for certain use cases.
With tools like Ionic (first released in 2013) and React Native (first released in 2015) it is easier than ever to build hybrid apps with native-like components. Hybrid apps are now faster, less buggy, and able to interact more deeply with the native UI.
The threshold for hybrid app performance is substantially higher than just a few years ago, but there is still a point at which you may need to develop your app in a native language.
Original Answer:
Yes, the general sentiment is that Hybrid apps are inferior to Native
apps. While this can be frustrating for developers more familiar with
web technologies, it does come for good reason:
Inability to interact with native components: Although plugins such as cordova-plugin-statusbar exist, there are limitations
interacting with and manipulating native components using web
technologies. One great (and frustrating) issue I have personally run
into is the inability to have an input at the top of they keyboard as
the keyboard animates in. This sounds like a nonissue until you look
at an app where this is an essential feature such as in a chat app
like Slack.
300ms delay: Although modern browsers are beginning to phase this
out,
the fraction of a second delay present on Hybrid apps makes the app
feel slow and non-native. This issue is becoming less of a factor as
more users adopt workarounds such as
FastClick.js and some
frameworks such as Ionic eliminate it
by default.
The haters are right (sort of): While Hybrid app development has come a long way, there are still minor glitches and laggy
functions that are just not present in a Native app. Screen
transitions, app switching, and battery life are still common areas
for bugs to appear and likely will be for some time, even if they are
starting to become less and less noticeable.
There are some great Native solutions: With newer languages such as Apple's Swift it is becoming easier to
code in a Native language. That being said, tools such as React
Native fall into a gray
area between Native and Hybrid by allowing developers to code in
friendly technologies such as JavaScript but compile into native code.
The moral of the story is that it really depends what is important to
your specific use case. Hybrid apps have become a viable option and
are no longer an embarrassing side show. Conversely, there are still
minor aspects of interacting with the Native UX that are not yet
possible except with a Native app.
Overall, I recommend mapping out your project and determining if your
app needs any of the benefits of a Native app. With tools such as
Ionic View app it is easy to put together a
basic mockup of your app and test on a real device whether or not a
Hybrid app will work for you.

There's also AppGyver Steroids that unites PhoneGap and Native UI very well.
With Steroids you can add things like native tabs, native navigation bar, native animations and transitions, native modal windows, native drawer/panel (facebooks side menu) etc. to your PhoneGap app. Basically, anywhere CSS + JS don't cut it, Steroids reaches into the native layer to perform the action.
Also, with steroids, you can (although you don't have to) use multi-page architecture (multiple webviews) rather than single. With single page apps, all things like transitions are just CSS workarounds, and as Mani said, even modern tablets and phones aren't fast enough to make them smooth. It's always obvious when it's a phonegap app, especially when you've got a bunch of processes going, or if you're scrolling since JS processes are haulted (being fixed in iOS 8).
Using the multi-page architecture means you get 100% native performance (because those parts actually are native). And unlike phonegap, you'll get consistent user interface behavior and easier debugging (with a single page app, it's often difficult to recreate a particular state in your app). Multi page makes it far easier to develop and maintain your apps since your codebase stays cleaner.
Check the demo: http://youtu.be/oXWwDMdoTCk?t=20m17s

I also find a every good article here http://www.comentum.com/phonegap-vs-native-app-development.html, it compares these two ways in different categories.
The summary is as below:
Design of Interfaces (Same)
Cost (Hybrid has Advantage)
Development Timeline (Hybrid has Advantage)
User Experience and Performance (Native has Advantage)
Maintainability (Same)
No Limitations (Native has Advantage)
Security (Same)
Support and Resources (Native has Advantage)
Tools and Debugging (Native has Advantage)
Platform Independent (Hybrid has Advantage)
Popularity (Same)

One overlooked of the great options here is development with Xamarin.
Though it doesn't help to utilize OP's web developer skills, it has many pros compared to PhoneGap and almost no cons.
Xamarin vs PhoneGap Pros:
Mature framework providing access to the most (if not all) native
features of mobile devices.
Learn only one language (C# for the most developers) for all mobile
platforms.
Have a performance of native apps on iOS/Windows Mobile (since app is compiled into the native code) and very close one on Android (it still compiles to a native APK, but has to have a thin wrapper that translates .NET class library API into Android classes API at the runtime).
Maintained by Microsoft which supports the overall generous quality of the
platform itself and development tools. For instance, you will use Visual Studio and it's probably the best IDE around and now has free Community edition with every feature available that you'll need for Xamarin development.
Xamarin vs PhoneGap Cons:
Needs some time investments for pure web developers to switch to C#
and Xamarin class library API.
Therefore, Xamarin is a very solid option for cross-platform development nowadays.

Downsides of using Appcelerator Titanium (or equivalent)?

At our company there is a huge push for cross-platform (iOS and Android) development. Appcelerator Titanium is being considered (and seems to be the only thing that's being considered) to achieve multi-platform development without extra development time.
Everyone here can think of reasons to use Titanium. For reasons against using Titanium I guess the performance of the resulting "native" app from Titanium may not be as good as an app written in Objective-C for iOS. How significant would the difference be? Are there other reasons to not use Titanium (or equivalent)?
Note: I may write Titanium but reasons may not only be Titanium specific only. All reasons in support for coding in platform language (e.g. Objective-C, Java) qualify.

The Good:
Can create iPhone apps using very simple Javascript.
The Bad:
Apple has been rejecting some Titanium apps due to private API calls but Appcelerator hasn't responded to requests for help, nor updated their SDK. http://developer.appcelerator.com/question/123785/app-has-bee-rejected-by-non-public-api
"Native Widgets" are used, but only nominally: there's a layer of
logic and abstraction between them and your code; and this layer
changes their behavior and reduces their speed. The difference is
visible in the Showcase apps.
API docs are perpetually out of date. (no process for refreshing).
A wiki was created, which is becoming out of date. Editing only
allowed for employees.
Github projects do not have wiki enabled.
Appcelerator isn't true open source: they do not accept contributions from the community: The
titanium_mobile project on github has a long list of open pull
requests.
The help forum software has many technical & design weaknesses.
Email notifications from the help forum often do not work.
Staff rarely answers questions in the Q&A forum. Haven't been seen
in months.
Showstoppers appear continuously in "all the little gaps":
Correctly displaying images on the iPhone 4
Correctly loading images in a scrolling list
Although the platform does simultaneously support iOS and android,
the library/framework does not. A lot of runtime testing (if/then's)
is needed in apps that will work on android and iphone.
Continually releasing new products but not fixing existing products
and website problems. The "new" products are announced while in beta
and release candidate phases.
"Chat with Sales" app not attended to.
Appcelerator does not take down outdated training videos.
Stretching the truth and bait-and-switch with pricing: a 30% sale
only applies to yearly memberships, not month-to-month. The blog
posts & marketing materials do not state this. Only upon checkout is
this shown.
[Seen 8/13/2011] Another way in which Q&A forums are broken: The order of
results for a search is trashed: each page of results orders its hits
from oldest to most recent, at the bottom of the page. Go to the next
page of results (i.e. 51-100), and again, the 1-year-old hits are
first, with 6-weeks-old at the bottom.
My Unanswered Questions:
[Seven unanswered Q&A questions not shown: I don't want to be personally identified by Appcelerator staff
and receive sub-par treatment.]
Results:
Am spending many hours trying to discover an API in the absence of documentation, and hacking to discover workarounds. This time is wasted, and would have been better spent simply learning to make apps in XCode & Objective-C.

How significant would the difference be?
AFAIK, Titanium will generate Objective C, so unless their stuff is woefully inefficient, I wouldn't expect speed to be a major issue.
Are there other reasons to not use Titanium (or equivalent)?
Well, that depends on how you define "equivalent".
Personally, when I get into cross-platform apps, I expect that I will use PhoneGap. That's for one reason: standards.
With PhoneGap, you're writing HTML, CSS, and JavaScript, as if you were writing an HTML5 offline app. All PhoneGap does is turn that into an installable package (e.g., APK for Android) and give you opt-in proprietary APIs for getting to device-specific stuff. Their expectation is to simply fill in the "gap" between what HTML5 on mobile supports and what native apps on mobile supports. Heck, it's even in their name. :-)
As a result, what you are writing is the same sort of tech you would use for a Web-based app, and it may even get to share some of the client-side code. You can use whatever you like from mobile frameworks (e.g., Sencha Touch, jQuery Mobile). And, if someday app stores support HTML5 offline apps, you might even be able to drop PhoneGap altogether, if you're not heavily dependent upon the device integration features.
Titanium lets you write in JavaScript, but the standards compliance largely ends there. You're using proprietary APIs for everything, including the whole UI. Personally, I'd rather back a more popular horse -- HTML5 in this case, more so than PhoneGap specifically. If for no other reason, it'll be way easier to hire HTML5-savvy developers than Titanium-savvy developers.
Neither PhoneGap, nor Titanium, nor any of the plethora of other options (e.g., Rhodes, Flash/AIR) give you all of the device capabilities. These engines will vary in their extensibility -- I know that PhoneGap has a plugin model, that Flash/AIR is pretty much only what you get from Adobe, and I'm not sure about any others.
Titanium has one advantage: you get a near-native UI, instead of an HTML-based UI. (I say "near-native" because some of their widgets do not necessarily have native equivalents on all platforms, so they roll their own as needed) For some apps and some audiences, that alone may tilt things in Titanium's favor.

Titanium/iOS specific answer, my 2c.
Native iOS vs Titanium
PROS
It's nearly as fast as native for most things.
The time needed to write a working prototype it's way shorter.
If you need to integrate javascript legacy code or libraries it will work provided that it doesn't use the dom.
Your javascript code needs to be well spaced and to include semicolumns where needed or the compiler will complain and eventually abort the build.
You can use Coffeescript or any other language that compiles to js
Automatic memory management is top notch, getting the same results in objc is always time consuming and sometimes debugging intensive.
You can write your own modules in native code to extend Titanium's capabilities.
It's open source.
They recently changed their support offering removing the 5 app limit, much more affordable.
You can change a view js code while running the app in the simulator, you will see the results when you reload the view you're editing. That's a boon :) (exception: there's no way I know of to reload the code in app.js)
CONS
Debugging is a pain. Haven't tried out Titanium Studio yet, it might be a big improvement.
Adding too many views tends to degrade performance faster than using native code.
The Titanium Developer app on Mac has plenty of interface glitches and you might find yourself restarting it pretty often.
In some versions the print to console debug statements are broken.
You will often stumble into cross-platform abstraction leakage.
Support on the forums is a bit light, many issues you will encounter are not big but still annoying.
Need to pay attention to JSON correctness, the included parser tends to be picky. Using eval is always an option.
Compile times and loading in the simulator are not that fast, titanium objc is pretty big.

Compared to Xcode, Visual Studio & even MonoDevelop, Titanium Studio feels slow (real slow), buggy (restarting several times each day, even reinstalling a few times) and of course you've got to deal with JavaScript... We found that the pain of developing in Titanium was too great, especially when you have competent iPhone & Android devs around so -
We looked long & hard into the best option for cross-platform dev & ended up using Mono - Touch & Droid. It's been great, we do actually share 80% of the code between iPhone & Android, & we're just beginning a port to WP, which is going well (again sharing 80% of the code). Of course it's not a miracle fix - you still need to know how to develop for each platform. I've even grown to like C# almost as much as Obj-C now :-)
Obviously, some will disagree.