Hi Daniel,
I'm assuming here that you're asking for a comparison of esri's native application APIs, also known as the ArcGIS Runtime APIs: Android, Java, iOS, Win Mob, WP7, & WPF. In the past, each API has had differences in what it offers, but over the last few months we've really focussed on making each of these APIs equivalent in the functionality and performance they provide. The goal of this is to make sure that, wherever possible, with the 10.1.1 release you really do just need to choose the platform you want to deploy to (i.e. Android, iOS, Windows, etc) and let that determine the API you use. Having said that, each platform does have different capabilities, so you'll find that the ArcGIS Runtime SDK for Java and for WPF contain more functionality that the ArcGIS Runtime SDKs for Android/iOS/WP simply because Linux and Windows are currently more capable platforms, particularly when it comes to accessing local data and resources. If your targetting the Windows Dekstop platform then the ArcGIS Runtime SDK for WPF is the best choice.
Cheers
Mike