I don't think it would be a blow out. Hatton would be a very tough fight for Miguel, but I think Cotto would take it out. Cotto is actually an effective boxer, for those of you who have seen his earlier fights against the likes of Cesar Bazan and even Abduleav. He can box and move effectively when he wants to, and this is what I would expect from him against Hatton. To use the ring, pick his shots and stay tight defensively. Eventually I think the cleaner harder shots of Cotto would wear him down, although you can never rule out the tenacity of Hatton.
Cotto is stronger,faster,has more boxing skills,better combos, all around movement, better jab, better fighter period.
I don't know why people are even mentioning the fight at 140lbs, because Cotto doesn't fight at that weight anymore. Hatton would need to move up to 147lbs. Hatton would put the pressure on, as he does with all his opponents, and Cotto would be too strong. He's physically much stronger after moving up and settling into 147lbs. It would be a great fight, no question. But Cotto would dismantle Hatton down the stretch.