Depends on how technical savvy you are and what features you want. For the average person who knows only the basics in computing, then I'd say go for the iPhone. It has an extremely user friendly interface, but is still powerful enough to do your computing. However, if you know what rooting your phone is, without having to look it up, then you may want to go for the droid. You have much better access to the underlying system and can tweak it like no other. Also, if your a programmer and don't have a Mac, then the Droid is the way to go since it is much easier to develop for.
The other thing to think about are features. I really wanted an actual keyboard instead of the touchscreen, so the iPhone wasn't even a choice for me.
As for apps, at this point the iPhone still has more apps, but all of the ones you would want are either on both systems or an equivalent of the app is available, so I wouldn't use this to decide.