I give Halsey a slight edge due to size and wrestling, but I think people are overreacting to the TIto loss and Halsey's last win somewhat. The difference in weight won't be as huge for this fight, and Halsey has historically been raw with his bjj. I mean he had instincts to go for subs, but he didn't quite know how to pull them off. The sub of Cooper might have signaled a permanent improvement or it was just fluky. We'll eventually see what the truth was.
Also, you have to factor in this is a 5-round fight, and Halsey has shown gas issues against Yager and to a lesser extent Pacheco at 185. He's been more surviving at the end of some 3-round fights, not thriving. And now he'll have 2 more rounds to deal with a terminator. If he doesn't get the early sub, he may be in troub.