But the "data" is the same. The running length is also the same. The only difference is how it is recorded onto the disc (more specifically, the rotational speed of the disc). This only aides in pausing still images (among other effects, such fast forward, etc.) The "Faces" set was the last version created just prior to the SE's, and as far as I can tell, has a cleaner picture (not by a tremendous margin, but it's there.)
Of course, my Def. Col. ROTJ set shows some occasional "spotting", easily seen in darker scenes. It's not horrible, but my Faces set has no visual problems. It's also easier to record, having only two discs (and my 701 has auto-flipping...much easier to make one big .avi file - 30 Gbs!)