Spence is most dangerous for Crawford - 50/50 type of match. Crawford would defeat the rest. I doubt Brook will be back at 147 - retired or 154.......
Garcia and Porter are very easy work for him, Thurman and Spence might be interesting. I'd favour him over both for now.
I would take Spence over Crawford, especially after his showing versus the sloth known as Postol. Why run from such a slow ****ing fighter? It boggles the mind. Spence on the other hand has that killer instinct that is almost extinct from boxing today.
He does look like a true 140 lber. Thurman, Spence, and Brook would likely easily handle his power, and Crawford could be pushed back by their strength and power. But what weaknesses or vulnerabilities has he shown? None really. He's one of the best movers and thinkers in the game. Thurman would be chasing and throwing haymakers while Crawford slips and slides and counters and pops him with jabs. Spence and Brook would be trickier, but I think Crawford beats them all. Luckily for Crawford Arum's guys Pac and Bradley would be the easiest fights of the top guys, but they'd also be the most exciting fights for him.