>>4487323I've shot with Nikon (albeit CCD), Canon, Leica, and Fuji (40MP).
In my experience it's been Leica > Nikon >> Canon. I won't speak to Fuji since I used it in a particularly bleak and snowy winter period so everything was virtually B&W in real life anyway, but from what I've seen of the simulations, they're purely a gimmick.
Canon is passable but the 'muh colors' is a meme. Going from a 5DIV to a previous gen Leica mirrorless has been a total fucking renaissance for me. Maybe I'd be happier with a 5DII/III but the IV (equipped with a 24-105L) produced files I found hard to work with in many cases, pic rel being a random example