Apocalypse Now
Theatrical all the way. "Redux" lags really badly - it's a chore to sit through rather than a treat. Never seen the workprint.

Alien
Theatrical as well. The cocoon scene slows the pace down too much, and while I like some of the other additions to the DC, I wish some things hadn't been cut out. This one's more of a toss-up, though, I could watch either and be happy.

Aliens
Neither. I prefer the Special Edition overall, but hate the scenes on LV-426 before the Marines arrive. I guess I'd go with theatrical, but I do really like most of the Special Edition, so I have to say neither.

Blade Runner
Final Cut. I may be biased as this is the only version I've seen in a movie theater, but I don't care. It's pretty much perfect IMO.

Terminator 2
Special Edition. Theatrical feels stunted and incomplete. Admittedly, the SE is a little bloated, but I'd rather have too much of a good thing than not enough.