I think it would depend on several factors. I was once a dedicated Canon fan, until I went to purchase an auto focus camera in the late 80's. Guess what, none of my lens would work because they changed the mount. (several times over the years). So when it came time to buy a DSLR, I went with NIKON. Bought a D200 and used it well for over 5 years, then bought a D810 and a few pieces of glass, including an angle finder.
I think both make great cameras. As for aftermarket service, though I've no experience with Canon repairs, Nikon needs to up their game in a serious way. My angle finder wouldn't hold position so I sent it in for warranty repair, two months later I'm still calling to find out the status and had to threaten to write Nikon's president to get a replacement, the service agent acted as though they could care less. Finally received it back after 9 weeks. Then, the eye piece cover chipped when my tripod was knocked over. The piece comes off with one screw and flips out, making for easy replacement. However, Nikon won't sell you the part, authorized service centers say it violates their contract with Nikon to sell the part.......so they wanted me to ship my D810 to them, pay for insurance and shipping (both ways over $120.00) and charge me labor to change out a part that takes less than 30 seconds to do so. Finally sourced the part on EBay. So, both companies make great products, but if you buy Nikon hope it never needs service.