FYI - I plan to spend another week with the EOS R, and use it more intensively, next week while I'm in FLA shooting. I ended up renting from lensrentals.com since Canon CPS has shortened loaner time to 6 days (incl transit back!), so not even a full shoot, so I'd have expensive overnight FedEx getting it back. I can bill my client for the rental, but not the FedEx for the loaner. A no-brainer as to which way to go. I'll give an update on my thoughts later.
As for the "Sony mount" controversy, It's like arguing about Nikon vs. Canon, and now Canon vs. Sony. All three companies are very capable and have a lot to offer. It comes down to preference for me. I've never really cared for Nikon (going back 40 years to fil days) and nor do I really care for Sony. Unlike some, I don't have to money or luxury to jump shit every time a different manufacturer comes out with something. Canon has served me well over all these years and continues to do so (even if I do get frustrated at times with their conservative turn), and I have never failed to do a shoot because of my equipment -- EVER. Now if you want to talk about my own failures, or back in the day when a client forced me to shoot EPN over my preferred Fujichrome, that's another story.