I don't think you can go wrong with an iPhone or an Android device. Obviously, if you decide to go down the iOS path you don't need any help, but if you're still considering Android, you should probably investigate these five phones:

http://gizmodo.com/5906041/five-best...es?tag=android

And remember, the Samsung Galaxy S III is being unveiled early next month.

Also, if you have any specific questions about the differences between iOS 5.1 and Android 4.0.4 (ICS), I'll try and answer them.