I think since Artwork for me is the most important, Censorship has to be second since it compromises the hell out of the first.
I can even stand full screen movies- a cinematographer went to great lengths to put EXACTLY what you are seeing on screen, know that just above are dozens of lights, and just below are tape, sandbags and tracks- thats like slapping them in the face.
Since I'm not much of an artist myself...I could only imagine how much more painful it is to see any detail compromised.
(that and, I've bought 2 hentai vids off ebay and was pissed as hell when they came super mosaic-ified (im talking more mosaiced than usual, it was awful!, ended up buying the domestic ones as soon as i saw them somewhere)