Diving catches often mean that the guy screwed up with his judgement to begin with.
On the topic of the argument, I think that Wily Mo's offensive numbers would go down if there was a larger sample size, because he would strike out more often. They need to gradually work him into a starting role to see if he can make more out of his at bats. He is all or nothing right now, which isn't particularly what the Sox are looking for. He doesn't need to be Youk, but just needs to do something other than home run or stikeout. Coco is the better defensive player, but its mostly due to consistency. It has nothing to do with spectacular plays. If you leave anybody with decent legs out there long enough they make some plays.