Probably with your background windows phone is a better option to start out with. Silverlight would be easy for you to get into. Each platform has it's advantages and disadvantages. Google's lack of control and 'free' view makes it hard to sell apps; and I know of no one making a living from google app sales. 85% of app sales happen on the Apple platform. But, with Google you'll be making some money with 'ad views'. Unfortunately, windows phone market share has been shrinking. Less than 4% right now, but less competition for app sales. Then you have Microsoft opening their windows store next year... could be some money there. I think your platform strategy should revolve around your overall career goals. If you are looking for a job, .net + windows phone may be doable. There is a demand for both iPhone and android developers for actual paying gigs as well. If you are going to try to make a living with apps, iPhone is still tops. I don't see that yet with Android. Although, maybe amazon will help with making the store experience more appealing for android users. I have read that windows phone is making money for some though. On apple's platform, this is the order of top earners: mac apps make the most, followed by iPad apps, then iPhone apps.

Cheers, Shawn Arney iOS Professional Developer & Trainer Learn iPhone Apps at: www.LearnApps.Org