That is exactly where I ended up. D850 and D500. I'm still in the honeymoon period with the D850 and only around 7k clicks. But from what I can tell, the D850 does hold up better in IQ. The AF still is slightly better on the D500. In good light and fairly low ISO you can not tell a difference between the 2 cameras when you shoot the same subject at the same distance with the same lens and crop both to the same size. The D850 shines though when you would overstuff a DX viewfinder though.