Usyk. He has faced a larger number of big hitters. I also think Usyk gets caught more than Bivol with big shots since he is a primarily front foot based fighter. Bivol primarily fights on the back foot and i don't think he gets hit as much.
Usyk 100%. As much as people like to wax lyrical about Olek’s skills (which are considerable) there are a number of instances when those skills would’ve been all for nought if he didn’t carry the beard that he does have.