Yes but RF35 1.8 is not better than EF35 1.4LII with adapter. I am comparing apples to oranges but so do you due to different decades where the products (50mm and 85mm) were made.I will never understand why people on forums often take a statement of personal preference as a statement of universal truth. herein2020 has explained at length and quite plausibly why he/she does not want adapters in his/her personal workflow, here for instance. Still, you keep insisting that adapters have no drawbacks whatsoever, you simply ignore all of the plausible arguments. It might well be that an adapter is perfectly fine for many people, and this hasn't been doubted in any way, but for herein2020 it is not. Why is that such a problem for you? Concerning your last post: I think there is enough evidence that one can "read somewhere" that e.g. the RF 85mm f/1.2L is optically superior to the EF 85mm f/1.2L II, and the same goes for the RF 50 mm f/1.2L vs. the EF 50 mm f/1.2L. You don't need your own optical bench to come to that conclusion, just read some of the dozens of reviews out there.
The RF15-35 vs EF16-35III would be more apples to apples comparison and they would come close to each other. They even have the same vignetting issues.
Having said that, personally I would like to avoid adapters for the hassle of keeping them, searching for them, having to use and remove them etc. Some new expensive lenses have also the IS advantage (24-70 and 15-35) and that's why I got them.