Usman probably takes it. As much as he appears to be on the decline, we haven't seen his cardio take a hit. He can still go for 5 rounds, that being said JDM's best bet is to go to the body early and often and try to suck the wind out of Usman.
Not to mention, JDM still occasionally makes some beginner's s mistakes when he's grappling. Dropping for a guillotine against Usman is not going to work out very well. Unless he's had a huge improvement in his defensive wrestling since the last time we saw him, I think Usman has to be the favourite here.
I guess this also means we are getting Leon Edwards vs Sean Brady in London, which I am not enthused about at all.