I know one of the reasons MPEG is favored is because surfers think they are superior AND the fact that most every surfer can play them no problem while WindowsMedia causes some problems with surfers not having codecs etc.
But on quality I really think WMV is as good or better.
Here are two similar movies in terms of file size.
One is a movie posted by FTVGirls, 30 second WMV movie, movie size is 640 x 480, file size is 3.9 MB. Second movie is :33 seconds long, size is 560 x 384, and the file size is about 3.5 MB. According to SobeGirl Eric, it's a propietary codec he developed called SuperMpeg.
Play SuperMpeg Demo Play WMV Demo
Good comparison because the movies are fairly close in byte size.
Forget about the content, which one do you think is better quality?