I would love to see this fight happen in about 2 years. Give Berto some time to improve (especially defense) Personally I think someone like Berto is Cotto's worse enemy. You can count on some bombs landing in this fight and both guys hit VERY hard, both have questionable chins. There is no way IN HELL this fight would go the distance. Two strong guys that throw hard crips punches that like push there opponent back = bombs away. I just think Cotto is going to run into trouble when he fights a fighter with one punch ko power cause Cotto is going to get hit regardless.
Berto isn't a 1 punch KO guy though. He accumulates punishment and wears guys out. His chin is much more questionable than Cotto who has taken shots from Ricardo Torres, Zab Judah, Randall Bailey, and Shane Mosley. He's been hurt, but has only been down once after staggering around the ring against Torres. Berto has been down and hurt from a single uppercut at the hands of Cosme Rivera.
I see your point, after thinking about it I agree about Berto's punching power, I think him and Cotto are on the same level when its comes to punching power. However I dont agree with your assesment on chins. Cotto has been rocked SEVERAL times, actually I haven't seen 1 fight of Cotto's recently that I wasn't thinking holy **** Cotto's about to go to sleep (great recovery though). Berto's 1 KD was a flash knockdown by a punch he never seen coming and he was up at a 4 count, Berto also "from what i've read on hear cause I haven't seen the fight" exchanged blows all night with Estrada without being effected, eventhough Estrada isn't a huge puncher I think it shows that Berto has a reasonable chin.
I would say Williams but I don't think anyone will fight him at 147 and he'll have to move up. So I pick Cotto.