Thank you Steve. One of the main reasons I was goi... (
Yes, and I still stand by my FPS statements :) - there is a noticeable difference in some scenarios (i.e. action) between 12 and 9 FPS. There are SOOOOO many times I have exactly ONE perfect shot (wing position, pose etc) from a 12FPS series with my D5 that I may not have grabbed with a slower camera. The extra 3FPS gives you 3 more opportunities every second of an action sequence to capture a perfect pose.
As for the larger pixels, yes, they do can have an advantage too. If you don't need the resolution (and, let's face it, most people don't - I unhesitatingly print 20x30 from my full frame D5 images), then it's a good option to consider because there is a noticeable difference at higher ISOs. The D5 is about 1 stop better than the D850 and 2 stops better than the D500 - not insignificant. However, as one poster mentioned, the D5's low ISO dynamic range is lower than the D850 (and I think the D500), so when I don't need the D5's speed, I often shoot the D850 when working in brighter light. I also like the D850 files better - I think they just have nicer color. Tools for the job I suppose. However, that love for the D850 files ends at higher ISO - the D5 retains better colors after ISO 2500 or so.
Some other D5 advantages:
Buffer - the D5 has a 200 shot buffer (as does the D500) vs the much, much smaller buffer of the D850.
AF system - The D5, D500, and D850 share the same AF system - and in general it's hard to tell the difference. However, after shooting tens of thousands of frames between the cameras, I think the D5 is actually a touch faster with initial acquisition in a fast moving situation and a touch better at hanging onto a tricky subject than the D850. The D500 is somewhere between the D5 and D850.
Less Mirror Blackout - the mirror mechanism gets out of the way faster in the D5 than the D850 or D500, which means you see the subject better during action.
Recall shooting - the D5 is the only Nikon with this feature: https://backcountrygallery.com/nikons-new-recall-shooting-feature/
Extra Function Button - this seems minor, but if you like assigning buttons to help you shoot, then the extra one is welcome.
Better Covers - Minor but the D5 has better battery covers and memory card covers then the D850 or D500 - plus the D5 has duel XQD slots with is really nice.
And finally, it just has better ergonomics in my opinion. The integral grip is wonderful and the D5 actually is a tough smaller the the gripped D850. It's also more durable than any other current Nikon and can really take a beating (I know LOL).
Still - I'd wait for the D6 - it'll bring all of the above and then some to the table :)