I know there's a Festivals board but this isn't really specific to festivals, more of a 'which band is better' kinda thing.
I've only got two real clashes where i can't make up my mind. The main one is Arcade Fire/ Biffy/ Battles/ Peeping Tom. A year ago I'd have definitely gone to Biffy, but I'm not that arsed now. However, I've not seen them do the new album live so it's still tempting. Battles have such a good live rep and the album is pretty good, Arcade Fire were the second best band I saw all festival when they last played, and Peeping Tom, well, it's Mike Patton, isn't it? I can't choose between them!
(The other one is CSS vs Nine Inch Nails...)
Any other major clashes for anyone?