CO wrote:
I have a D750 but have not upgraded to the D780 because the additional features are not ones I would use a lot. The D780 adds an on-sensor, back side illuminated, 273 point, phase detect autofocus the same as the Z6. It gives the D780 much superior AF for video. The D780 also has focus stacking and 2,359,000 dot resolution LCD screen as opposed to 1,229,000 dot resolution for the D750. A downside to the D780 is that it doesn't have a built-in flash.
I do not shoot the D750. But I do shoot the D810. When the D850 came out, I wanted one. It seemed to have some advantages for night sky work and a few new features in which I was interested. But there was (and remains, really) not enough difference to call it a real upgrade...more of an update. So I bought it as a second body and have been happy ever since. The only thing is that it has become my primary full frame, and the D810 is the second body. I'm happy and life is moving forward.