hi,
did some testing, but not just for pdp (quicktime) but also for gem (avi, mpeg): if you don't care about hd space, then rawvideo (YUV 4:2:0) is, in my opinion, the best codec for quality and it's not agressive on the cpu. but i never tried to open it in pdp so i don't really know if it's supported.
for gem, mpeg2 give me good result at 640x480, but on linux you cannot use the mpeg3toc to loop the movie. i don't think it's fix (i will try with my new distribution (gentoo), who knows)).
keep us updated, patrick