Though we can develop the i-phone application in the X-code
Why we need to use the Airplay-sdk?
can anybody differentiate between them?
I use Airplay SDK (see www.immortalcode.com) and it works well. Their code has been evolving, but it is pretty solid now. The big advantage for me is to be able to keep my source code in C++, and to be able to use a single code base for multiple platforms. I have built multiplatform games (iPhone, Android, bada, Windows) all from Visual Studio on Windows. The main caveat with Airplay SDK is that you may not get access to all the functionality you would normally have on a given platform. In particular, you probably won't get the native UI look and feel, and you may not have important options like using the ad provider of your choice. My understanding is that they've recently made strides in opening up the full range of native APIs on iPhone and Android, but still I think there will likely be problems when it comes to certain highly platform dependent stuff. Again, working with certain ad providers comes to mind as the main example.