While I adore my R5 (and 5d3, hate the r62), I just bought an s9 after pitting it against a a7c and z5ii - the last 6 months full of research. This body proved I can get the core photo + video features that i wanted in a small body, without getting stuck in crop.
I took the s9 out last night for the first time - and had a joy of time using something...well different, and full of features canon will never*(?) give you. My shooter friend is going sony for other reasons - zv-e1 because he is focusing on small form factor, high quality/cinema video and AF. He also has a r5 and r8- so that says something there. The canons lens jail has pissed us off royally. The sigma BF inspired me to seek out a small FF body to get that Iq jump I always knew I wanted vs. canon crop. (That said, my m50 and m62 have treated me
very well and will not be retired.) I can move the histogram anywhere i want on the screen, overlays for multiple ratios, and a metric ton of ui/function options. Nice! Even the way that you can change the size of your focus point with the control wheel is nicely done.
The S9 basic design isn't great at all, but the features are sublime. In comparison, my m62 has been in a smallrig cage for a long time- and i immediately bought one for the s9 to solve its abysmal handling otherwise. And aside from the lens hood, its the same general size profile as the m62 with a smallrig cage and a 11-22 for example. Man I love that setup, the cage makes it into a different experience.
I'm not building out a new system -
the goal / my use case was a SMALL ff walk around 50mm. See I've been stuck shooting my 50 1.4 at 2.8 for over 10 years....wider than that and it becomes very unreliable. Well..now I am shooting at 1.8 and everything is sharp all the time, and easy access to luts/ lumix labs to cut down my editing times and shoot directly towards moods. Also to be able to try out lenses- sigma especially - that I simply did not have access to as a canon shooter. I did not go with sony as the a7c does not fit the design I was looking for (m62 /sigma BF) style body.
I can concede that L mount has its own lens selection issues - however the smugness of canon and the direction they took with the long overdue 50mm 1.4 guaranteed that another OEM was getting my money. Having access to all sigma glass was priority, and hopefully the tammy 35-150 will get a L release someday. But for now the goal was reached.
That all being said, I freed myself from canon lens jail.

ALL sigma lenses are now in my purview, and that feels WONDERFUL. Maybe one day I'll go sony if they produced a body that I want and exclusively place a 35-150 on it. Z5ii is fantastic but also does not have access to sigma ff lenses. and its not compact. My canon loyalty was rewarded with the weak RFS line, no re-release of my beloved 22f2, expensive AF lens prices, and the 1400.00 covered up busted optics 50 1.4 ripoff debacle. Life is too short to keep waiting on canon anything. Get the tools you need/want and get your work done. Fin.