Yeah, this particular experiment doesn't reveal much because the Nvidia driver is a black box. We know in the past it used its "composition pipeline" in Wayland situations, and that was a particularly noticeable increase in latency. Plus, for a while the Nvidia driver also was stuck on software cursors. And even on the DRM path the big two compositors only updated input once every frame, which was the reason for it "to have much worse input lag."

edit: I should also point out the mouse acceleration curve, which if you don't fix it is different between X11 and Wayland compositors. That really messes up the "feel" of things.