From personal experience, I can tell you developing for Android is a lot easier than the process iOS/Apple puts you through.
Also from the Android perspective, being able to do ad-hoc distributions for testing is as easy as emailing your .apk to the person you want to test it, or hosting it on a fileshare service.
I also prefer an environment where applications have a common store and aren't "siloed" from other apps or the underlying OS functionality. For those reasons and more, I think the balance is shifting to Android globally.
The "siloing" of apps on Windows phone is one of the huge advantages with it.
Sure, writing apps for android is easier, but it is also more prone to errors and susceptible to hacks/attacks/etc.
Remember when Windows finally introduced memory protection (virtual memory, where each process has its own virtual memory area is is unable to write to another process memory range) back in the mid -90's. It was frowned upon by some developers but now we can all agree that it was a step forward.
Now, finally Microsoft are isolating the other key aspects of a process (we had cpu and memory and now we get storage and network, and a few more twirks).
This advance will solve a lot of problems that we today solve with virtual machines (talking servers here), which require that we run an additional full OS instance for each application/WM we have.
Well that was two two hour lectures condensed into 5 sentences.
Bottom line is, Android/Linux will follow and if it doesnt it will perish within 10 years.
/GoK