I think Mares wins based on experience with elite level oposition. He fought the best at bantams (Although the best was missing) of an era people considered to be one of the best bantamweight eras ever.
In a fighting scenario, I think Santa Cruz can win. Eventhough he's still learning he's a pretty smart guy with those hip shots. He knows how to position himself when the ref can't see them, maybe he does it and Abner tries to get even. Since he's more blatant with the low punches so he might get some warnings and maybe a point deducted. So in a fire fight, this benefits Santa Cruz a lot.
Tough fight to call I like Santa Cruz more though so I would WANT him to win.