You come across an interesting compromise here:
1: Android and IOS are both fairly easy to develop for, but Android is FAR cheaper. If you are doing a one-man app, it may not be in your best interest to spend $299 a year to get Apple's package. Plus, to even develop for them, you have to own a Mac computer.
2: Both groups have equal return on app sales, (so far) but since Android is an open-source project, you might see a change. Apple and Android are around 70% return (in Apple's case, 30% goes to Apple, the rest goes to you, and in Android's case, 30% goes to carriers and the rest goes to you.)
3: IOS has by far more apps. As of June, July, and August, IOS has around 225,000 apps, with over 5 billion downloads, and 57,000 app/update growth per month, and Android has around 100,000 apps with over 1 billion downloads and 10,000 app growth per month. Android has a higher percentage of free apps. As of July, 57% of Android apps are free, and 28% of IOS's apps are free.
4: I personally suggest Android. Even though the market isn't huge, there is no cost to develop, and there most likely won't be for a long time. However, not all devices running on Android have all the features of the others. Unlike Apple, some devices may not have GPS or an Accelerometer, so plan your apps accordingly. If you are willing to spend money with Apple's Developer Program, then I suggest doing both. You'll get the best of both worlds, not to be cliche.