I didn't see all of them, but I did see Porgy and Bess, Follies, and Evita (and Godspell, FWIW)
As you pointed out, it was effectively a race between Follies and P&B - I don't recall any of the others being serious contenders for the win. Follies even won the Drama Desk IIRC.
I loved Follies, but personally I think they got it right with Porgy and Bess. I thought that revival was magnificent, and my appreciation for it was cemented even further when I saw it on tour - which is to say, it held up even without that Broadway cast. So when you add that extraordinary cast into the mix, it makes the win feel all the more earned.
Follies was likewise a major event - it was a lush, beautifully-designed production, and there were a ton of excellent cast members. But I think it suffered in a few areas. First of all, I know I'm in the minority here, but I was underwhelmed by Burstein's Buddy (the beginning of my ongoing reticence toward Burstein as a performer, which continues to this day), as well as Ron Raines. I actually liked Bernadette's Sally more than most people did, but I agree that the vocals weren't all there. And as for the production, I liked it at the time, but having since seen the National Theatre production, I realize just how much the Memory Ghosts were wasted in the 2011 revival by comparison.