This isn't asking who you think or want to win, this is asking who has a higher mountain to climb, thus them winning would be more impressive than the other guy winning. This can be answered without being biased. I am a die-hard Yankees fan, but even I must admit that them beating the Twins in the first round was a lot less impressive than if the Twins had beat them, because the Yanks were expected to win. They were the favorites. They were considered the better team, with better players. Now, while I wouldn't consider Cotto the better fighter per se, I do think he has a tremendous advantage due to his size, and to the fact that he has been in with and handled guys much bigger than Pacquiao very well. The size and strength difference are the reason why I think Pacquiao has a bigger mountain to climb than Cotto, so a Pacquiao win would be much, MUCH more impressive, while a Cotto win would be due to him beating up a smaller guy who hasn't spent nearly as much time at such a high weight. This is the classic David vs Goliath story....
Well Cotto is the underdog so if he wins its huge but if pacquiao wins we know he can hang with real welterweights