Davis takes a lead going into the midrounds but Marquez dissects him and stops him late... Or maybe close decision for Marquez.
Completely different styles. Not really comparable. I tend to agree that Marquez wins, though. Davis was a physical talent, not much more. No passion/heart in what he was doing. That said, his negative style and cat-quick hands/feet would likely make Marquez look bad for the majority of the fight, even if Marquez was doing the better offensive work overall. He probably wins a clear decision in an unimpressive affair from both ends.
Knowing how Howard was, and how he didn't really accomplish anything at the super lightweight ranks, I think Juan would use pressure, score a couple of knockdowns, and take a close decison over the passive Davis.