yea winDVD has slightly better picture quality (only noticable on larger screens) I had it on my laptop but switched to powerDVD because winDVD kept freezing(1 out of every 2 viewings at least), even after a fresh OS re-install. winDVD occasionally (1 out of every 20 or so viewings, just enough to get on my nerves) does the same thing on my desktop, so I replaced it with powerDVD too and the problems went away.
in retrospect, on my old pc winDVD(the next last version) ran perfectly. I don't know if it's a flaw with the latest version of the software or what, but it's the only program on either system I have persistant issues with.