Hmmm, even in greatness it's a tough comparison. Cotto was never really the man at any weight, but definitely more consistent and many more big fights than Forrest. Forrest was the man for about two fights then quickly loses the title and pretty much went under the radar until his fight with Mora which didn't cause to much fanfare either. I think Forrest was the better fighter, but Cotto the greater fighter. 12 round UD for Forrest in the fight. Cotto will go down as a much greater fighter, especially since he still has some history to write.
Cotto barely edged out an old worn out Shane, I honestly don't see this being competitive at all. Vernon could not only punch but he could box as well.
Forrest wide UD. He wasn't a power puncher, and Cotto was relatively solid at the weight. If Margarito takes 11 to stop Cotto, brutally beating him along the way, I can't see Forrest doing it in 12. He would definetely beat Cotto though.