WMV is your best bet. btw, WMV will be smaller in file size, so that means it's cheaper to serve and - important here - faster for your members to download. plus WMV streams so your members won't have to wait for it to start playing. there are a few guys who can't see it - but unless you're serving MPGs, there are always going to be a few guys who can't see your movies. and MPGS aren't self streaming so you'll displease more members who are not used to waiting for movies to download.

and quicktime may be better quality at very high quality, but when used in paysites i mostly see quicktime vids at worse quality because quicktime files are so much larger. at a normal web size and speed, WMV can look very good.