I always assumed because the NTSC version of Star Wars is sharper than the PAL version the same would be true for Empire and Jedi. But I was just comparing the NTSC and PAL version of Jedi and I think the opposite may be true. Looks to me like the PAL has a tiny bit more detail and is sharper. It also looks to me the PAL version has less "ringing" so maybe the "ringing" is introduced by the mpeg2 encoder settings. But I just compared a few scenes so I'm not sure yet this is the case for the entire movie.
I also assumed the PAL version was cropped a bit more at the top and bottom. Apparently I'm also wrong about that.

NTSC

http://img150.imageshack.us/img150/908/clipboard02mr3.jpg

PAL

http://img357.imageshack.us/img357/4476/clipboard01mu4.jpg