I would not say winamp is any better or any worse than other apps at auto-tagging. I will say that you can influence the results just by changing the tags/filename, etc.
the audio fingerprinting it does is pretty light. I think musicbrainz and some others are more indepth. here are some interesting links:
http://musicbrainz.org/doc/Fingerprinting
http://www.codeproject.com/Articles/...fingerprinting