I didn't read the whole thread, but my choice is defenitly MW.
Not just because it's my favourite live song...
1. The idea of the first encore on vertigo is "achtung baby songs/back to zoo tv" theme. So let's keep it in mind and the third song should be also from this era. IMO the next song should be EBTTRT/wild horses/uteotw/MW or just another song from achtung baby(/zooropa, but I can only dream
), NOT from JT! Anyway- WOWY just don't flow right with zoo station/the fly sang by a Bono in his "15 years older The Fly" persona.
2. IMO MW is far better live, especially the solo in the end is incredible. This time WOWY is even without extra snippets like "we'll shine like stars in a summer night" or "nothing will tear us appart". WOWY without these verses is just not complete for me, it's like MW without the ending solo. Not right...
3. Dear joshua tree fans
- you get four songs from JT: ISHFWILF, bullet, WTSHNN, RTSS (now it's gone, but it was in the set during almost whole tour till now). Not all fans want 5 songs off JT to be played, really! Even if U2 don't want to play MW and if they really need to play WOWY, drop other JT song and play a song from other album.