Against a typical fishy player I think he's likely donking a weak ace into me or is on a bluff. I think I raise the turn, as I'm going to get paid off by a weaker ace on the turn and river, and he's likely check/folding the river anyways if he's on a bluff.

Against a good player I just call down, bet the river if checked to. He's less likely to pay off a raise with a hand that we beat. But I'm kind of puss like that.