Okay, regarding photography these days, I don't fancy myself much of a photographer. but it wasn't that long ago, my partner and I ran a sports photography business that used canon cameras, and i can tell you this, having either of these cameras then would have been an absolute dream. I literally have nothing to say about these cameras from a photographic capability standpoint. And as someone who naturally finds problems with everything, take that to mean the highest praise the R5 easily trades blows with the sony A7R IV, which II call the best photo camera for the money.
These canons are fun to use, offer great handling, have terrific lenses, focus reliably, they're just fantastic. When the EOS R came out, you had a decision to make between it and the 5D Mark IV, and in many ways the DSLR was better with these two cameras. There's no decision to make anymore, they're better than the EOS R, and they're better than pretty much every other canon camera say for maybe the 1DX III. But it looks like the R6 might even be using the same sensor as the 1dx Mark III. So you really are getting canon's best here.
Of course, if you're all about photography and can afford the bigger price tag, the R5 is the better camera, it drives just as fast as the R6, but with more detailed images, a nicer LCD screen, and a higher resolution viewfinder. And a lot of the complaints that i made about video don't carry over when you toggle a photo mode. Now you do have two card slots, now your ibis is very good, I was getting four to five stops of improvement on an 85 millimeter manual lens. And although taking photos affects your record time due to heat, I couldn't get the camera to overheat while in photo mode. So i don't think that'll be an issue even if you're firing high burst for long duration.