Interface

The iPhone 4S is running iOS 5.0
The Galaxy S2 is running android 2.3
I personally think that the iOS interface is easier to use and can be faster. But that has a downside; there are not nearly as many options as on android. The android market also has apps that apple doesn't allow. The two interfaces are very different and have their own strengths and weaknesses. It is really your choice and what you like better. For more info on the interfaces you can go here,
http://www.pcworld.com/article/219952/google_android_vs_apple_ios_feature_war_heats_up.html

Tie