Eh, I hate this question but I'm going to answer it. Both.
Some of the songs on the RE sound MUCH better than on the UE. Likewise, some of the songs on UE (like Elite) sound better on that.
The UE also has Fury (which I prefer on UE than on the site release, actually), Kaori, and Empire which are all fantastic tracks.
Frankly, they both rock and I'm glad I own them both. When I pop in a CD to listen to Redeemer I normally pop in RE to be honest because some of the tracks sound better and the ones that I prefer on UE arn't that big a difference (again, Elite sounds great either way). Then I sometimes pop in UE and listen to Fury, Kaori, Prelude & Empire.
They both rock, they both have kick-ass art, I'm glad I own them both. I'm glad they both exist. I wouldn't change squat about them, I have both discs and love them both.