For cross-platform it's not about the code you write IMHO. It's about HOW you build applications. The two alternatives you offer (Xamarin and JavaScript) are two two totally different approaches - native vs. hybrid and HTML vs. native UI created in designers.

The choice really comes down to: Do you want to build apps using native code and essentially design for different platforms multiple times or do you want to use HTML and design once and run on many devices as you do with Cordova. Using the former you get full platform fidelity, with the latter you do not, you're limited to what you can do with HTML including non-native feeling touch behavior.

There are pros and cons for both technologies, but making this about programming languages of all thing is just plain wrong... anybody can learn languages easily enough - the platform and build is what's hard to understand and even figure out what is appropriate.

+++ Rick ---

>There's really no advantage of one over the other. Pick the one you're more familiar with. If C#, you'll also use Xamarin. If JavaScript, you'll also use Apache Cordova (formerly PhoneGap)
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>>Hi All,
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>>Microsoft says VS 2015 will support cross-platform thing. So I think I would develop applications for Windows 8 store and IOS same time. It sense good for me. Which language do you advice me? I see C# and another option Javascript + CSS + HTLML5. I really don't know anything this Javascript stuff but I understand I can develop Windows store desktop applications too other than web applications. Which is better for Windows store. C# or Javascript. Which is more easy? Can I develop serious business desktop applications with Javascript if Javascript is more easy than C#???