I've both cards. Pretty much a toss up. The Audigy is a much better gaming card (although the latest Santa Cruz drivers narrow the gap abit) and it does have alot of features the Santa Cruz doesn't. This might be a significant advantage if game developers start using the new EAX Advanced HD features and there's no reason why they won't, considering how quickly they jumped on the EAX bandwagon when the SBLive first came out. Also, despite the complaints, I've never found any problems with the Creative drivers and PlayCenter 3.0 is actually an excellent (and fast) CD ripper.
The Santa Cruz on the other hand, sound incredible when playing music or .mp3's and in fact, does feature hardware .mp3 decoding when using players that support it (ie. the included Audiostation or MS Media Player). To me, it's very noticable hearing music reproduction from either card and if you're into .mp3's and similiar audio entertainment, this is certainly the better card to own.
Personally, I'd be hard pressed to give up either one (which is why I have both

).