I'm not an Apple product die-hard, but when I was considering all phones before buying my iPhone 4 (a year ago), the iPhone seems a level or two above all other phones in almost every way. Sure their proprietary nonsense is obnoxious sometimes, but not enough to matter too much. My thing was, if I'm paying for the expensive data plan, I want the best type of phone, and so far, I think that's the iPhone. Who knows what the iPhone 5 will be like, but it's almost for certain that it'll have a slightly larger display.
Galaxy S3 is already out,I don't know about your country though. It has amazing features apple doesn't have yet.But like NoTomorrow said,if you're used to apple products and apps,go for iPhone. But I would go for Galaxy S3.