Here's a very partial reply (because I don't know the full set of answers), just to get the discussion started... my comments are only about OUTPUT...
I have a PCI Delta card, as you do. I also have a Creative "Extigy" USB-connected sound device, with 5 speakers attached to it (4 bitty ones and a subwoofer).
I only use the Delta as my output driver when I want to route sound out to the analog equipment I still have here in my studio. To make cassette tapes, etc. -- or when for any reason I want to hear the output through my external stereo system instead of through the computer's system.
Otherwise, I always use MS Sound Mapper, which drives the Extigy quite nicely, including properly supporting a 5.1-surround mix, which I cannot play through the Delta.
I'm curious about those OTHER drivers too, though -- and I'm looking forward to someone else's comments about them.
Ernie
Let's approach this from a "as a video editor which should I use?" point of view.
AISO, which has been nicely described by Spot already are geared towards low latency during multitrack recording in the audio/music realm. For example you want to record your guitar as you listen to previously recorded drum and bass tracks and you want to hear the previously recorded tracks in real-time with NO lag and play your guitar part exactly in time. This is of no use to a video editor and since AISO have the nasty characteristic of not wanting to share with other apps. simultainiously this presents problems if you open another app. that you have assigned AISO drivers to also.
Microsoft Sound Mapper uses the card that has been assigned in Windows Control Panel > Sounds > Audio (XP) Multimedia (9x). This does not expose all the cards and their outputs in Vegas and also uses DirectX to do math on the fly I believe.
Direct Sound Surround Mapper is virtual and is similar to the above I believe concerning calculating on the fly.
Windows Classic Wave Driver (MME) in a Video editor's and many audio editor's situation would be the best choice. You have all your ports exposed to Vegas directly.
WDM (Windows Driver Model) is similar to AISO in terms of latency except it shares nicely unfortunately it's not supported by Vegas yet.
I don't have an authorative answer on this but as no one else seems to either...
I'd say none at all, its not usually the role of a driver to be messing with the data, just woking out where and how to send it somewhere.
For example if you've got an AVI file with DV in it being sent to 1394 port the driver takes care of how to get it to the appropriate hardware, it doesn't 'understand' anything about the DV data stream so has no way to fiddle with it. It's codecs that make a difference to audio / video quality.
In the case of soundcards they're usually hardware devices. The quality of them is what affects the quality of the audio.
Of course if the driver is sloppy and cannot feed data fast enough them you'll get real nasties in your audio, I'd say much more dramatic than dropping a frame or two of video.