RS,
> Is there any difference between the two cards in this feature? <
Yes, and the choice is not easy. The SB Live works well but has a lot more hiss than the Audigy. But the Audigy has too many MIDI playback bugs to be useable! I finally got rid of my Audigy and now use LiveSynth Pro with Sonar. There's now a new Audigy 2, though I have no idea if they finally fixed the bugs.
--Ethan