Between BtB and FFXII, I'd first ask if there are any other options so we can make a fully informed decision. Next, I'd ask if you've played a fair bit of either of them, in which case I'd suggest the game you've played more of, just to get it over with.
Beautiful Katamari: Beat. I fail at dashing, but luckily that didn't matter.
Pocketbike Racer: Have you ever wanted to drive around on a little bike as the King from the Burger King commercials and shoot a subservient chicken with rockets? Me too. The game was a cute little promotion that came cheap with a combo meal at BK, and I managed to find a copy in my local game store for $5. Five tracks and the usual series of kart powerups (shield, boost, forward shots, mines, blinding, seeker) make this an average game, but it's much better than it could have been.
Shadow Complex: Got me a jetpack. Now I just have to transfer it to the real world...