I agree with most of what Kevin stated. For me it as a matter of weight. My D850 with the battery grip was heavy. At 80 years old, was a bit of a chore to climb in and out of locomotive cabs with it. I have the Nikon Z7 which has the same resolution as the D850 and is a lot lighter. I have a Z7ii coming next week. It has dual processors and is faster than the Z7. I have not had a problem with the EVF but I have heard that some do.
The new Z lenses have been ranked better in most cases than the comparable DSLR lens and I was in need of new glass anyway. I have the Z 14-30, 50mm 1.8, 85mm 1.8, 24-70 2.8 (yesterday), 70-200 2.8. i have the adapter and kept a few of my F lenses....200-500, 105 macro.
Been a Nikon guy since my first one....Nikon S3 Rangefinder in 1961. Since Nikon was the standard camera for the Air Force, Navy, Marines, and Coast Guard and I was an Air Force photographer/photojournalist and used them at work, only made sense. When I was an instructor in the Air Force photography school taught the Nikon F2.
Cameras are tools and people like and use different tools.