Well they are both awesome, as you have witnessed. you've played them both, so you will probably be happy either way. My pick is rock band. you probably have halo or halo 2, so even though they aren't the same as the third, you still have a first person shooter to play. Rock band is unique (well there is guitar hero) so it will be a great addition to any gaming collection. Plus, Rock band is more fun to play with friends (in person, not online) in my opinion, and honestly, take a look at all your games and ask yourself, Do I really need another violent gun game??