If he truly believed he'd win, and even KO AJ, I think he would. 1) Because it'd be bigger money. 2) Because with a KO he could claim to have done what Usyk couldn't across 24 rounds. 3) Because he'll claim forever that he won tonight, and #2 would help him build a narrative that he was robbed and really the top dog of this era. Fighting Usyk again is riskier - firstly because the odds look against him winning, second because he'd have to do it twice to really make that claim and third because at the age they're at now it'd probably always be seen that Usyk won clearly when both were in the best shape of that trilogy... It's a much bigger mountain to climb, IMHO, and I'm not sure he can dig that deep. We'll see!
Usyk is the easier mark at this stage; agreed. I do think that Joshua would have been easy work years ago, and his three losses have done nothing to change that opinion for me. Now, though? He could easily outbox AJ... but AJ can catch him on the chin and then it's night night. I think that Fury can beat Usyk, honestly, in the same way that I thought Hearns was better than Leonard, even after getting stopped.