Seapy- After reading about the difficulty of processing D850 images, I am rethinking my decision to go with the D850. The D810 and, based on some comments Akira made, the D750, are now back in the mix. Used D810s can be found on Ebay for around $1250. The D750 is a little less. I’m not sure whether the increase in iq from my 20mp D500 to a 24mp D750 would get me where I want to be, so I need to read a few reviews and then perhaps come back and ask some questions before I buy.
Sorry for going off topic. Arthur, I went the other way, swapping the D750 for the D500. My primary reason was that I had serious reliability issues with the D750 and after it failed a third time in less than 70k actuations, I just didn't trust it anymore.
I shoot primarily birds, night/starscapes and some daytime landscapes, general wildlife and a fair amount of aircraft.
For birds, the D500 is undeniably better. The same applies to aircraft in flight, from the ground. In these applications, the crop factor more than compensates for any IQ loss except in very bad light, and the improvements in handling, speed and especially AF performance are very welcome.
For daytime landscapes (assuming you have lenses that deliver similar results on the different formats), I think there is little difference between the two, although the D750 has slightly more pliable files, but this is easily compensated nowadays by doing an HDR.
For star and night landscapes, the D750 is the clear winner, and is probably even better than the D810 in some respects (primarily the pivoting LCD makes this form of photography much easier), but I suspect in image quality the D810 will win, but the D850 should beat that too...
I would love to suppliment my D500 with a D810, but would not swap.
But I attended a talk by a couple of SA's most prominent nature photographers. One of them (Wim van den Heever, if you want to look at his work) stated that in his mind the D850 is currently by a long marging the best nature camera in the world. He has replaced all his cameras (D5, D500 and D810) with a pair of D850's...
When shooting birds, using it in crop mode gives equal or better performance of the D500 in almost all respects, while delivering similar file sizes to the 24MP cameras...