The theatrical cuts for me. Those are the versions I saw and fell in love with. Besides, the stuff added to TUC was distractingly awful; the Scooby-Doo ending to a plot that didn't make any sense (why put a human in a rubber mask when there are plenty of Klingons in on the plot?); Valeris sliding down that damned pole and hitting the rubber wall; "that Klingon bitch"; "Admiral Cartwright" BONNNNNG!. Totally ruined the film for me and I grew to hate it. Seriously. Then I saw the theatrical cut again and loved it. Those few minutes made all the difference. There was enough cheesy stuff in the movie, it didn't need any more.
Star Trek II: most of the additional scenes are pointless ("that young man, he's my son!" - pause until Spock enters frame - "faaaaaaascinating!"), but the Scotty stuff was great.
I will admit I like the DE of TMP better than any other version, but the theatrical still has great stuff the DE removed. It's still a favorite of mine.