If you're always going to be playing with a group, it sounds like Rock Band is the way to go, but if you're going to end up playing solo a fair amount, Guitar Hero III might be the better way to go. Also, how hardcore are you? It sounds like Rock Band's difficulty is a bit lower. From what I read, it sounds like both games are a lot of fun, though. I had Guitar Hero II, but I didn't have the patience for it at the time, and I gave it to my sister. I figured I'd get III if I got the itch to try it again.