Thought this was interesting from atu2 - Edge talking in Rolling Stone...
"We'll play about half the album, and having played some in TV appearances, we know these songs translate well live. There's a few that will be up there with our best-ever live songs. Some of them we really have to rework -- 'Crazy Tonight' was a very keyboard-oriented song on the album, but I took it to the guitar live, and it sounds great. You make all these discoveries, and next thing you say, 'Oh, shit, we should have done that on the album.' Steve Lillywhite says we should record our album, put it to one side, then go on the road for a year and come back and re-record it [laughs]."
Makes you wonder at times, I love the recorded version but it gives you insight into the band's creative methods too I suppose