Tron. As others have said the differences are almost entirely cosmetic. Tron Pro is a complete game.
I do agree about XMen to some extent as far as game play goes on the pro (I don't like the moving ramp and nightcrawler was a little disapointing so really only the spinner is a big downer on the pro) . . . that said both the XMen LE backglasses (Wolverine or Magneto) are easily the best two backglasses Stern has released to date . . . I don't think there is anything even close to those two mirrored backglasses . . . they are stunners.