nah u can do winner stays on on battle mode or something at guitar hero rock bands only good when u have 4 ppl who go in hissy fits when they can't play at that precise moment :P
Rockband is definitely better then Gh3, because Guitar Hero has only guitar playing against other guitars.
As a response to Shlibub: There are tug-of-war and score dual features in rockband. So, actually there are more interesting battles, like between singer and drummer.
Personally, I think that Rock Band beats Guitar Hero 3 in music choice as well as graphics and overall feel. That said, Guitar Hero 3 is the WORST edition of Guitar Hero to come out. But I still think that Rock Band is better overall. Sure, there are areas where it can improve. But Rock Band beats Guitar Hero 3 by far. The only downside of it to me was the cost.