This may sound like I'm taking the easy way out, but I just don't see a bad decision between the 5DIV and D850. These are two incredible cameras that can use really any piece of glass a photographer would need in their bag. It comes down to personal preference for UI/menus, how the bodies feel in your hand and maybe even what part of the world you live in--some countries have easier access to either Nikon or Canon gear.
Sure, there are other factors like video features or partiality to certain lenses one maker has the other does not. Maybe you want a 105 1.4? Nikon is the only game in town. For real estate photographers, maybe the TS lenses of Canon really are that good?
Can one concentrate on the disappointing parts of each body? Sure, I guess. Having to add a battery grip to climb from 7FPS to 9FPS seems like a big PIA to be honest for the D850. And that the DXO score of the 5DIV lags THAT far behind the D850 is always a fun discussion on this forum. Are either of these factors deal breakers? Hard for me to say, but these are certainly two of the best DSLR bodies ever made.
Sony's stagnant A-mount line kills comparisons for the a99ii according to most bloggers/vloggers, but rest assured it is an incredible body in its own right with the luxury choosing auto-focusing Zeiss glass. Eye-focus AF is fantastic, IBIS makes every lens stabilized, AF system is potent and IQ from the 42MP sensor borrowed from the a7Rii is somewhere between the 5DIV and D850. EVF (no filmstrip effect I've noticed) saves a punter like me, and the outstanding shadow recovery is the cherry on top. The battery life isn't great, but I did shoot the Orange Bowl with an a77ii with juice left to spare after 1700 frames. Not sure if the a99ii can duplicate that feat, but I suspect it is in the neighborhood. And the a9 seems to deserve the hype, with what I've seen from guys on this board like MedicineMan4040, Mystik610 and others off the board like Paul Nelson and Patrick Racey-Murphy. The wildlife shooters hate the lack of fast, long glass but it doesn't seem to stop MedicineMan from producing on stunning BIF image after another.
The completely jaw-dropping assortment of full-frame bodies on the market right now is a real marvel. Nobody really even really talks about the Pentax K-1, but there's another outstanding body with top-notch IQ. Pretty much the only disappointing FF body that has come out semi-recently has been the 6Dii, and to me that was a real shocker. The original 6D was a tool that only needed a little sharpening, and somehow Canon didn't get it right.



