I have nearly nothing left in Nikon F mount, but I have found myself wanting to buy one/both cameras for no real reason - they would be overkill for what I am able to shot these days.
My thoughts exactly. Rationally I do not need any of these. Financially I can afford both of them. My eyes are so bad currently that I should better think about a system with image review in an electronic finder like Fuji or Sony or Olympus.
After the first euphoria I know I do not need to hurry any decision.
I bought the D3 six months after it came to market, but I never needed her speed. I needed HighISO, she delivered. I needed robustness, she delivered. I needed prestige for some customers, she delivered.
Today? I am not sure. I am very happy with the D600, very happy with my 360Precision-Kolor-Panorama setup, very happy with my Sinar-tabletop-setup, very happy with the D3 as a portrait camera...
What can get better with speedy AF and fps? Nothing in what I currently do. Rationally I take the 8.000 Euro instead and ask some professionals to build a better multi channel customer acquisition system for food photo customers. Then I try the D850 as soon as she comes out as a better Digiback for my Sinar-contraption and reduce the D600 as a panorama/archtecture body.
Gosh. Emotions!