Hi, I like you gave it a lot of thought regarding which one to buy! I went with the R6 because everything I read said it had the same auto focus system , same fps etc, also the better buffer size too all made me choose the R6 .
I have had the camera for two weeks and have shot around 1000 shots & cannot say anything bad about this camera.
The ergonomics are superb, the EVF is excellent, also I don't need 8K video, and saved £2000!
I shoot aviation mainly and I have used a 45 megapixel camera before & my MacBook did not like the huge file sizes, and the storage issues.
I also read that for online publishing you cannot see a difference between 20 & 45 mix on screen.
I probably would have wanted say 30 m pix but the best Pro sports camera the 1DX MKII had 20mpix as well.
Hope this gives you some help.