I think a lot of people might have argued that Brook had one of, if not the best, jab of any active WW going into the fight, and taking everything into account, Spence's jab was the more formidable weapon in their fight.
It should be noted that Pacquiao, even in a performance where he battered Algieri from pillar to post, rather regularly had trouble cutting off Aligieri's space. It's a big reason why he failed to stop Algieri, I think. Granted, that's always been a weakness for Pacquiao, but Spence didn't have any trouble doing it against Algieri from the very start of the fight. It wasn't because of some nebulous "athleticism", it's because he has good footwork.
He obviously thrives on the front foot, but he showed even for periods against Brook that he can box on the backfoot and use his jab to reasonable success. I was saying it because it suggests versatility (not particularly common versatility even at the top level).
The big shots that both men landed involved timing Porter and catching him as he lunged in. Both caught Porter coming in with their best shots. Obviously Thurman and Brook are different fighters and work a bit differently, but the point is that both regularly timed Porter and landed flush with some of their best punches, and both men's punches had similar effects. I don't see a considerable difference in power between the two.
Not mentioning Spence's infighting ability when talking about his skill as a boxer seems like a fairly glaring omission. He's as good as anyone in the sport at it. Of course, to get inside and make use of that infighting ability, cutting off the ring is fairly important, so I fail to see how his infighting ability being very good is necessarily an indictment of his footwork (that actually sounds fairly ridiculous).
Spence being near the top of the division isn't debatable. The only thing in question is whether or not he's the best WW in the world right now, and I think there is a pretty strong argument that he is.
