By my calculation, there have been about 130 million Android devices sold to date, and over 200 million iOS devices (including iPads and iPod touches). I haven't found an easy way to get these numbers. Here are my sources:

* Apple announced the 200m number at WWDC this year http://www.tuaw.com/2011/06/06/apple-touts-impressive-ios-nu...

* There have been about 325m smartphones (including iPhones) sold worldwide so far http://www.gartner.com/it/page.jsp?id=1421013

* Android has about 40% market share worldwide http://gadgetbox.msnbc.msn.com/_news/2011/06/09/6820706-andr...

It looks like iOS still has at least 50% more users than Android.

But none of that matters compared to the one number I find hardest to determine:

How much money is sent to third-party developers on each platform?

Meaning, how much do customers spend on apps, less percentages sent to the app store owners? The consistent feedback I've gotten from all Android and iOS developers is that iOS customers are willing to pay more. (Apple announced they've given $2.5 billion to developers at WWDC. I can't find the corresponding Android number.)