Disney promises the Ultimate Band experience on the DS
Of the two, the DS version definitely sounds the most interesting: it is advertised as a "rhythm-based music game with a built-in recording studio" that allows players to record guitar, bass, drum, and vocal tracks for original songs and mix them in-game. We're slightly wary, having been fooled by promising-looking Disney music games before. Both versions will use Disney's Dgamer social network ... thing.
We foresee problems when Disney decides to start making sequels to a game they've already labeled "Ultimate." Although Square doesn't seem to have had any problems in that area.