Shane would get outboxed but, he had enough power to really hurt Floyd. So I'm going against the tide and say that Shane via tko/ko late rounds. All he needed to do is land a few good shots to wobble Floyd before finishing him off. I think Shane will find that opportunity within 12 rounds he certainly had the speed.
I think in terms of pure h2h ability, at 135 Floyd must be very close to his best or even at it. Shane was immense there but imo better at welter when he first moved there, his style works better with that extra strength i think. The Floyd at that weight was mobile and i think that an attacking Mosley would get ultimately beaten on the cards. Just my opinion.