I like RB2 a LOT better (so much, in fact, that I bought it and about $80 of DLC). There's a lot of great songs in it, and a bunch of shitty ones, but overall, the library is far bigger than GHWT. There's some Yngwie Malmsteen, Megadeth, The Who, Kansas, Grateful Dead, and a bunch of other really fun songs.
Also, GHWT sucks.