i'm a user of both phones... gave my ip4 to my wife. obviously, i like sgs2 better. way better. and she even want to swap! lol.
when the hype dies down, people will come to realize ip4 is boring, unless you jailbreak.
one of the advantages of iOS is the apps. but iOS apps are ported to android as soon as dev earned much from iOS users. thank God for iOS users. its the reason android app stay mostly free.
user experience? not only sgs2 fast and smooth but its UI is highly customizable.