Joe
Hello,
This topic has been covered many times before and will attract nothing but fanboys cheering for their favorite logos. The answer to your question is simple: It's a matter of preferences.
If you have tried the 2 then you have a favorite. If you haven't tried the iphone then only by trying it for yourself will you find out if you prefer it over the SGS2.
Abstract questions about "Which one is better?" in general are not welcome here on the forum. On the other hand, if you have some more specific comparison then it could be accepted.
Example "Which phone has a better GPS?" Or "Which phone gets updated more often?"
Simply asking for which is "better" doesn't mean anything.