To me, the consensus narrative on NCFOM and TWBB goes like this: NCFOM was good, but TWBB is kind of like it and better. So TWBB wins out between those two (I've only seen the first, but if I were an Academy member, I wouldn't vote for it -- though artistically accomplished, it kind of left me cold).
Juno is completely different, so can compete without comparison. This could capture the prize if the Academy is in a "Little Miss Sunshine" mood.
It would be quirky-and-feel-good vs. epic masterpiece.