Both are great devices. It really depends on your preference over iOS or Android. They have similar specs and features, their screens are both beautiful and they are quite well built. The iPhone 4 has the "death grip" issue, but it isn't much of a problem. The only difference I see is the OS. So it depends which one you prefer the U.I, which appstore has the apps you want, which is more aesthetically pleasing, etc. I personally like the Galaxy S, but that's just me.