Well, for one thing, I do like the new Yavin sequence, so it would be nice to add in a "seamless branching" aspect. It would be easier to add in a DL project.
"How much better in picture quality are the SE laserdiscs than the OT laserdiscs?"
I've not seen them, so I can only assume they would be better overall. I'm much more interested in the 5.1 soundtrack, which I could render to separate waves, reinsert the original dialogue when necessary ("You're lucky you don't taste good"/"Alert my shuttle"), and recompile to AC3 and use for my DVD.
"By how much does a transfer from PAL to NTSC lower quality?"
I really couldn't tell you. I would assume that changing the framerate shouldn't be much harder than converting from 30fps to 24fps, but again, I've never done it.