Spinks is pure boxer with good speed and movement. Let's also not forget that he lost a close decision(one judge had him winning 117-111, another one had him losing 115-113) to a 6 "1 hard hitting middleweight named Jermain Taylor. So Willliams' sixe won't be a problem, his power won't be a problem, and given that Spinks is also a lefty, that won't be a problem either. Williams won't be able to outbox him, and he'll have a hard time getting in many clean shots. Spinks outboxes Williams in this one and pulls out a close decision.
I agree with you that spinks did a good job against taylor (i actually thought he controlled the fight and might have earned a decision), but taylor fights NOTHING like williams. Do you agree? And how can you say that since spinks is a left that won't be a problem, southpaws hate fighting southpaws. Cory just seems like he would spend the whole fight shitting his pants and not throwing, getting tired in the late rounds. I see the outcome none other than williams ud, based on workrate. cory is very quick and he has good movement but I dont think he could keep up with williams.
I only mention Taylor because of the size. Williams' biggest assets are his size, workrate, and handedness. Righties have more trouble with lefties than lefties have with lefties. They both would be at a disadvantage anyhow, so it would be a wash. So right there, the size and his handedness wouldn't be much of a factor in this fight. The only thing Williams would have going for him is his workrate. Workrate has a funny way of dropping against a speedy fighter with good movement. Corey's lack of power, and the fact that he doesn't commit to his punches could lead to him losing a decision. However, he would definately be able to outbox Williams and land more shots. I guess the judge would have a lot to do with who wins this fight. Personally, I would favor Spinks.