I know they exist but I have a hard time believing that the people who would sell any and all of their lenses for identical RF versions are the majority.
Listen to all of the complaints about the RF 400 f/2.8 and RF 600 f/4 being the same as the EF versions.
I think the point is that there are few 'identical' versions of RF lenses (not talking solely about the optics, more about the top-line features). The 24-105/4 comes to mind as an identical lens to its EF predecessor, and it's one of the few lenses priced the same. The great white 400/600 lenses are also in the 'identical' category, as is the 50/1.8. As discussed, the 70-200 zooms are much smaller and lighter than their predecessors. New lenses have IS (made less impactful by IBIS). The 100/2.8 Macro goes to 1.4x magnification. The 50/1.2 and 85/1.2 offer significant optical improvement. The non-L wide primes have are faster and have macro (0.5x) capability. The 10-20/4 is
significantly smaller and lighter than 11-24/4, and the former is actually cheaper as well.
I agree that only a minority or people would likely completely swap their EF lenses for RF, especially those of us who have many lenses. But the RF lineup will continue to grow, and over time the majority of people will progressively transition.
Personally, I initially did not plan to get the RF 100/2.8 Macro or the RF 10-20/4. The former came along at a price low enough that I decided to give it a try, and the focus shift issue that concerned me turns out to not be a problem in practice. I will likely pick up the 10-20/4 at some point, the downside is giving up the easy ability to use filters with the 11-24, but the much smaller size/weight mean I'll take the 10-20 along more frequently than I bring the 11-24. Still waiting to see what Canon brings for TS lenses, and also if they replace the MP-E 65.
While I'm not one of those who hates on the adapters, there's something to be said for native lens swapping. For something like the 600/4, the adapter is fine – that's a lens where my personal use pattern is typically a one-lens outing, so the adapter just stays on the camera and I swap lens/TCs. With just one EF lens on a multi-lens outing, it's also fine since the adapter just stays on the lens (e.g. when I went to Italy over the summer, my only non-RF lens was the TS-E 17, and I just put the drop-in filter adapter on it before leaving and that's how the lens traveled). But going out with a mix of EF and RF lenses means a lot of fiddling.
