I love my galaxy s3 and I have been very happy with it after have all the iPhone models. I love the fact that I can do more with it and add more memory, change my own battery. I dont have to worry about my phone shattering like glass if I drop it on the back.
Galaxy. The reason: Fast, powerful, great features, not so restrictive, more customizable. I don't feel like buying a phone that will be obsolete because a new phone that comes out a few months later that doesn't even have any new features in it (every iPhone that's ever been made). Just being frank.