Before switching from film to digital, I checked the offer on the market.
For me, Nikon DSLRs were specs-wise more interesting than the Canons. (As long as you are inexperienced in a new domain, specs seem to matter more than ergonomics or service).
But Canon had the 24 TSE II , so I bought Canon and never regretted it.
Then came the 100-400, my favorite, the TSE 50, 90 and 135...whispering to my ears (still saving for one of those!).
Conclusion: Canon did it right, unlike Nikon, to accompany the R's introduction with high-end lenses, neither soni nor Nikon have in their program.
It's the lenses that really matter (and the guy behind them, of course).
I know: the Nikkor TS 19mm is a wonderful lens too...
Nikon have the 500mm f/5.6 PF, which is at the moment a lens that can have its own body as nothing competes with it. Canon have a whole host of tilt shifts and the MPE65 which all warrant a Canon body. I mean it would be nice to go all in on Canon or all in on Nikon, but then I always have two bodies too. If you have a 600mm f/4.0 on your Canon R1 with a 2x converter, then a 500mm f/5.6 on a Z6 becomes a invaluable little extra if the subject gets too close or a wee fox gets curious.
For me I have been on Canon EF for over a decade. Nikon's Z mount and Z lenses look better for mirrorless and they have been giving wildlife shooters attention, so I have been seriously considering giving Nikon the decade then in 2030 maybe it'll be Sony or Fujifilm medium format mirrorless with 800mm lenses.