I am about to take the dive into the... rock(?) genre. Right now GameStop is offering the guitar+drum+mic+game for GH for $99, and Sears is doing the same for RB2. The defining factor was going to be compatibility with the upcoming Beatles game. Both claim to be fully compatible (at least according to a chart Harmonix released through Kotaku). Sooooo, I guess it comes down to... I don't know.

That's where the good people at Wiihacks come into. I guess I should add that selection-wise, I would take variety over tons and tons of hard(er) rock. Pennies for your thoughts!