Marquez, but I don't like the catchweight. He's the lightweight champion of the world, so what would be more impressive than going down to 135 and taking his titles. Wishful thinking because this would never happen in reality...(even though I'm sure Pacquiao could still make 135 without problem.)
So being realistic Marquez at 140. I think he's already shown he is ineffective at 145, he looked a bit fat and sluggish against Floyd.
That being said, it looks like this will be at 145. I definitely like Marquez best of the choices, he already has 2 epic battles with Pac and both have been on impressive runs since they fought last, plus he's still the best fighter being mentioned as a possible opponent.