I've found the Android API itself to be about on par with Cocoa Touch; some things are easier and some things are harder, but it seems to balance out. A major advantage for Android is that it uses Java instead of Objective C, giving you real memory management, no header files, and generally better built-in libraries. Also you don't have to muck with certificates nearly as much; apps can deploy to your phone immediately, and you just pay Google $25 (one time, as opposed to $99/year for Apple) and use a self-signed certificate to put it on the Android Market. And your app shows up on the market a few minutes after you upload it, and won't get pulled unless it's malicious.

For fun, Android easily wins IMO. For profit it's less clear; there are certainly more iPhone users, but it may be easier for a quality Android app to stand out. My paid Android app is earning around $10/day (before Google's cut), which from what I hear is on par with typical iPhone apps.