Android is kind of funny. For geeks like me, if Android and iPhone were cars, iPhone would be the basic model with AC and power windows, while Android would be the luxury model with cruise control, navigation system, leather seats with ass warmers, etc. But to most non-geeks, Android can be a bit overwhelming and a miserable experience if you end up getting the wrong phone.
Android is way ahead of iPhone in the different ways you can customize it, but if you don't know enough about the difference between the two that you have to ask, just get the iPhone. You'll probably be happier with it. It's not as functional as Android is, but it has far fewer ways to bite you in the ass
And if you can get a used iPhone 4 (as opposed to the 4s) outside of contract, so much the better, because there'll most certainly be another one this year with 4g built in.