I open saying it's understandable why a few others would choose Sony, like the A7R III. Even one of Canon's top people indicated that Sony makes excellent gear. My comments here pertain to my gear, wants and needs. I rarely shoot video, and do portraits and landscape photography. For a year or two, I've had a lingering question whether I should, or would need to, get a Sony or similar mirrorless in the near future, and what path Canon was planning to go in the years ahead.
So what crucified my questions about switching from Canon to Sony (etc)? One of the biggest factors was the new lenses and adapters than allow the EOS R body to accept the entire arsenal of native EF, EF-S and RF lenses. Canon released their first full frame enabling backwards and forwards compatibility. This means I can utilize all my existing Canon lenses, ones I enjoy a lot. Also, with Canon's new RF 50mm 1.2 is more than a clue what path the company is headed.
Canon put features in the EOS R that are lacking in the Sony. Canon omits some features, but none that hinder my photography. The features the EOS R did add, actually have some folks saying "hey, will Sony put that in their model". So the EOS R proves who has to keep up with who is a two way street. But for me, the important part is the EOS R has more than enough for my needs. I do prefer dual card slots, but given the rest can put that on the back burner for now. An amusing arena was focus points. I rarely use more than a handful anyway, but the EOS R has over 5600 -- it may be the camera we could nickname "The Undertaker" in this regard. It virtually buried future discussion about what company's camera has the most. After hearing a good number of reviews about the EOS R's effective focusing and capturing, I'd say the excellent ergonomics and backwards lens compatibility are two of the most important aspects for me. The image quality results I've seen shared leave no doubts in that regard.
Weeks after posting this thread, a photographer posted one of the best reviews I have seen so far. It made Polin or Northrup first videos seem "lab rat" or sterile by comparison. This review link is repeated later in this thread. Polin did a more thorough review weeks later, also shown below.
This one is Jared Polin's review after some hands-on time with the EOS R
I posted this video in post #73, and decided to add it here in post #1. The guy starts off slow for a few minutes, but he moves on to a decent abundance of UN-EDITED images that show focusing and color. A lot of the shots he describes as "crazy" sharp were from the new RF 24-105mm according to one of his replies to someone asking if they were from the new FR 50mm 1.2



