I'd say the Revoution would be the better choice for music (The reviewers say Revo is a better sounding card in that it is cleaner and more open in its reproduction while Audigy2 is overall warmer sounding and less dynamic). But frankly, I doubt if you can feel a tremendous amount of difference between the two with computer speakers.
Other considerations: Audigy2 has DVD-Audio support and has better gaming abilities to its defence. And if you plan to record something, the Revo will be better (although none of them are that suitable for multi-track recording).