Definitely get RB2. I've tried out the drums on GH which I thought were the only better option than RB, but they're terrible as well. On the few sets I've played the orange cymbal rarely hit and you had to slam it to get it to register those few times. Also, when you're going for rolls those...
Since LBP has a $15 gift card for buying it at CC according to the new sales ad for that week, can you get the $10 pre-order bonus and then the $15 card for buying the game?
I already have quite a few games and Rock Band DLC and would be willing to share them and join a sharing group. I have been burned before though so I'm a little skeptical of the people on PSN. Just PM me.
PSN: SithBen24