How is the low light performance of your R? I am waiting for the R5 to decide it vs a 1DX3 or Sony a9II. I know these are very different cameras, but I am trying to prioritize bodies? I have a 5D3 and its a bit slow for sports and low light is very limiting. I had the 5D4 at launch, but sent it back because at the time it was 1500 USD more than it is now. I shoot a bit of everything sports, wildlife and portraits.
Is the processor for the R5 going to be DIGIC X or something different?
The "low light performance" like AF performance or the noise?
I'm extremely happy with both on my EOS-R. The only issue I have is the EVF when shooting very fast action, like BIF. For this reason I bought the Olympus EE-1 Dot Sight and that took care of the problem.
I was also comparing the 1-DX III to my first-generation 1-DX and while the Mark III files look better at higher ISO, the difference is not striking, if that's what you expect. I would say, maybe one stop difference.
The AF on the new 1-DX is vastly improved though, compared to the first generation.
Now, get this: yesterday I was playing with stacked teleconverters on my EOS-R and my 1-DX Mark III. The TC's are the latest Canon generation (1.4x and 2x).
Of course, I had to use a 12mm extension tube to stack them.
To my huge surprise, the EOS-R was way better to achive focus and to keep it. Go figure!
When, and that is a big "When", the 1-DX Mark III focused on the subject, it worked really well but the EOS-R was much, much more consistent and accurate.
If this is what the image sensor based AF means, then the R5 will be a beast of a camera.
Anyhow, the 1-DX Mark III AF is a pleasure to work with in any other conditions.