Kicha Fisheye

Im a Canon camera guy but i'm honestly thinking about moving to the dark side and buying a Nikon setup. Whilst in the Solomon Islands I got to use my friends Nikon D850 with the new Nikon Fisheye lens on a few dives, instantly I was impressed. Seeing the 45 megapixel images on my 4k iMac screen and the detail in which my Canon is lagging isn't sitting to well with me. Canon's answer for a very similar price is the Canon 5D Mark IV which does not come close to the quality of the Nikon D850 - i've felt let down with the cameras Canon has been producing as of late, where Nikon and other brands seem to be excelling. Would love to know what you guys are using or what you think about this?

Anyway, here is a photograph from a dive site. Kicha in Marovo Lagoon of a sea fan. Using the Nikon fisheye at 8mm with a full frame body I am able to create a complete circle (this isn't photoshopped)

Nikon D850, Nikon 8-15 Fisheye, Aquatica water housing
1/50th, F10, ISO320