Usyk hasn't fought anyone of prime Wlad/Vitali quality yet. It would be interesting. I think Vitali would stand more chance of winning than Wlad due to style. I'm going 70/30 in Usyk favour.
I feel like we can get a decent window into how Usyk would fare vs the Klitschko brothers by looking at how the similarly-styled Chris Byrd did against them. With that in mind, I definitely see Vitali as being the more vulnerable of the two. Regardless of how people so easily dismiss Byrd's win vs Vitali, the fact is that Byrd completely took away his jab!! Not even Lennox Lewis managed that feat. Certainly Usyk, with even more reach and height than Byrd, would prove a problematic obstacle for Vitali.