Doom9.net - The Definitive DVD Backup Resource - Codec Comparison May 2003. The latest motion Codec comparison that I could find. Pretty interesting results.
Basically says that DivX 5.05 is fast and has OK quality while Xvid is slower with better quality.
I ran Xvid against Raiders of the Lost Ark and in two passes, it took a total of 11 hours (!!!), so I can vouch for not fast. Did have it set for very high quality though.