I was going with Dubois’s size to steal it, but then realised Lewis was nearly identical in size to him when he fought Mercer. I’m struggling to pick a winner, this could be a fight that’s decided by 1 point or so I feel.
I like the best version of Mercer by KO. I think Mercer can at least replicate what that sloth Joe Joyce was able to do. I don't think there's much of a difference in skill level between the two, but the difference in durability seems enormous to me. Mercer should be able to consistently land that jab, and he has plenty of power to hurt DD. Not confident DD can crack that granite chin of Mercer, and have doubts he's durable enough to last 12 rounds. Remember, Kevin Lerena had Dubois on skates, and nearly finished that in one round. Mercer seems the safer pick.
Prior to Dubois resurgence going on his recent impressive streak, I would've said Mercer in a close fight either by decision or late KO. He just did not perform well under pressure, sometimes pawed with his jab, and didn't always assert himself using his size to his advantage. Fast forward to the Miller fight and beyond, and Dubois is now a lean mean fighting machine. Power in both hands, good timing, has improved his combination punching, can cut off the ring or use lateral movement himself, keeps his hands up, and is a lot tougher mentally. The biggest difference between Mercer and Dubois is that Mercer is so inconsistent, a hot/cold fighter, while Dubois has been consistently excellent lately. I think Mercer still has the more proven track record when it comes to chin, endurance, and work rate as seen in his brutal wars with Cooper and Lewis. He'd give Dubois all he could handle at his best, but I think Dubois narrowly takes this.
His chin proved reliable untill age got to him though. He could lose a decision maybe to DD, that could easily happen.