Isaac in my opinion. He was stated to be Alara Kitans' equal by Alara herself and every time they've sparred that has been the case, as well as Isaac having some feats himself. He even overpowered Alara when her body started to deteriorate after being away from her homeworld's gravity for too long.
And Alara would thrash Data. Just...badly.
Yeah, Kaylons have been portrayed as physical peers to Xelayans both via feats and statements.
Also, he is rather amusing.