Rockband for sure, much more stuff to do not just guitar but bass, voice and drums too, makes for a much better game. plus the character creation kicks Gh3 to the ground
My problem with Rock Band is that it has no good songs, unlike GH. With GH you get really good classics, and some great new tunes, but I have not seen one good song on rock band.
I Like Both But RockBand Wins coz when you have friends at home its more funny no waiting tour for playing and etc etc but skill needin of the game for the guitare GH3 need more skill than RockBandwho is mostly concentrate about the drum coz we already some karaoke game :P
but in fact i already reserved my RockBand 2 and GH4 i cant wait to play it