(Note – I am posting this both on NikonRumors and CanonRumors). Two months ago I switched to Nikon after two decades with Canon. This is my experience going from Canon 5D4 (and 5D3, 5D2) to Nikon D850. This review relates to these models only.
With Nikon you get massive megapixels and speed in one camera. With Canon you have to give in to less megapixels for the speed (of a 5D4) or more megapixels but less speed (of a 5Dsr). The Nikon D850 is both models in one. WINNER: Nikon.
FOCUS ASSIST LIGHT
Canon was always better here and Nikon finally caught up. With the D850 Nikon has gotten rid of the obnoxious bright white focus assist light from previous models and put in an invisible infra-red focus assist light, just like Canon has always done and Nikon should have always done. WINNER: (tie).
The buttons on the back of the Nikon D850 light up along with the top screen when you hit the light button. Canon does not. I do a lot of night photography and find this feature invaluable. The way to turn on the light is also easier on the Nikon (flick the spring-loaded lever on the front of the shutter instead of finding a separate button on top for the Canon). WINNER: Nikon.
I do a fair amount of landscape and architecture photography where I need mirror lockup for the sharpest image. With Canon you have to find it in the menu and set it and go back in the menu to turn it off. It's a pain. With Nikon it is right on the top dial along with the other shutter settings (single frame burst, low speed continuous, high speed continuous). This is sooooo convenient it is almost worth switching just for this feature. WINNER: Nikon.
Nikon and every other brand except Canon use a simple single letter designation: S for Shutter Priority, A for Aperture Priority, M for Manual, P for Program. Canon uses this bizarre labeling system of TV for Shutter Priority, AV for Aperture Priority, etc (I had a student in a class think TV mode was for plugging the camera into their television). WINNER: Nikon.
There has been a lot of debate over this, especially since Art Morris switched from Canon to Nikon. The claim is that the focus tracking mode on Nikon is superior to Canon. After only two months with limited use I can say confidently this is true. I do a lot of zoo photography and even a big cat walking (not running) towards me only a couple out of the series would be in focus with 5D4. Most of them the head is blurry and the focus is on the shoulders. With Nikon every single frame is in focus. On a recent trip I even saw a leopard running and I quickly grabbed one shot before it was out of frame. I know my 5D4 would never react that quickly so I thought it would be blurry. Nope – the Nikon nailed it, with the focus right on the head. WINNER: Nikon.
It depends what you use. If you like tilt-shift lenses then Canon has a better selection. Nikon (in their effort to keep the manual F-mount) has had a bizarre progression so that only certain lenses work with certain cameras (and some with physical aperture rings need to be set a certain way). So for long-time Nikon users it has been a complicated road whereas Canon kept things simple (by changing to an autofocus mount). Since I just jumped into Nikon and only use the latest E series lenses, it's a non-issue.
A common standard lens for serious shooters is the 24-70 f/2.8 and it is mind-boggling that Canon's still does not have image stabilization. Nikon does (as do Tamron and Sigma) so IMO that is a good reason to go with Nikon. Another standard pro lens – 70-200 f/2.8 – is essentially a tie, though the Nikon focuses a few inches closer which I find useful. The Nikon 70-200 (and other telephotos) wins for me because it is black and not white. I hate white lenses for some reason.
There is one lens that Nikon has that no one else has and it is so useful that it is a primary reason I switched. That is the 500mm f/5.6 PF. Though not cheap, it's still about half the price of a 500 f/4. But the size and weight make it a must have in my book (assuming you need a long telephoto). PF is Nikon's equivalent of Canon's DO and it shocks me Canon hasn't done more with this. For the record, I ordered mine from a local dealer (Tucson Camera Repair) and it only took three weeks to get (not the months that it takes at big dealers). It is tack sharp, even with a 1.4iii teleconverter. But for lens lineup overall I will say: WINNER: (depends on your needs).
I have been interested in D850 since it came out and I knew I would like it. But I am shocked at how much more I like it than my 5D4. Combined with the stellar (and oh-so-portable) 500 PF lens, the difference is astounding. I feel like I have traded in a Ford Fiesta for a Lexus RS. (Disclaimer: this does not mean Canon is no good or that everyone else should switch. I am just sharing how the D850 meets my needs better).