Started out on Fidelity to get a taste of those maxed out graphics, but now I'm on Performance RT. And yeah, it does look a tiny bit worse - in particular, the fur that looks absolutely amazing in Fidelity mode looks a bit more noisy and less defined, so it loses a little of that CG look - but the smoothness of 60fps just can't be beaten, especially in battle sequences.
I would actually prefer 60fps gameplay with 30fps cutscenes if that was an option, because damn do those cutscenes look good in Fidelity mode. They really do approach Pixar levels, and you do lose a bit of that in Performance RT mode.