I think this is an interesting comment from one of my favorite wildlife photographers. I have been following his Back Country website hoping for a review of the D850. This is one of the last exchanges on his D850 blog:
Not sure about choosing this as a wildlife camera over the D500. If you want a do-it-all camera, then sure, but as a wildlife only camera? The big problem most of us have is that we’re focal-length limited. If you can always fill the FX frame, then great, but I know that I typically have to crop my DX shots from my 200-500mm lens. I’d be kidding myself if I thought I wouldn’t have to crop the D850 even more. When viewing 850 images at 1:1, they actually appear slightly noisier than the D500. No problem, right? We can just downsize that huge, 45 MP image. Well, again, if we have to crop a lot, the downsizing advantage disappears. I’ve seen a D850 DX crop and compared it to a 21 MP D500 shot, and the D500 shot actually looked cleaner.
So, if one is going to be cropping to DX size the majority of the time, I really think the D500 is the smarter choice. IQ will be about the same, and the D500 is smaller, lighter, shoots faster and is much less money. Just my two cents. Thanks for all your vids and reviews!