xvid is a bit better imo... and it is under the general public licence instead of the stupid divx licence... plus i think the xvid codec handles divx but im not sure about that
if you use anime suki xvid is what handles everything atleast... anime suki = not a bad database of torrents...
go xvid whatever though, in my experience wtih encoding it for personal movies stuffs (shrinking my family guy dvd to a size for my pda) xvid goes faster, and does the job better.
Anyways, open source stuff progresses faster in cases like xvid becouse theres alot of independent people that write stuff for them and submit them to the project for their own good/hobby instead of money. Basically what open source means is the developers care more about the goals of the project in general.