I did go from the higher resolution D810 to a Z6 and I'm pretty happy with the Z6, mostly the ergonomics.
What I like
- Most of my subjects are still, so I can care less about the viewfinder lag. I like the zoom feature of the evf, I have it bound to a function button.
- Full electronic shutter works great for my studio microscopy stuff
- I don't need anything above 24MP unless there's pixel shift
- Filter stack of the Z6 is something like 0.7mm, it produces crisper images
- S-line lenses
What I don't like
- Camera seems to sharpen the raw images
- I've seen many debayering errors when shooting resolution charts
- PDAF points show up when I pull the shadows out in a drastic manner
What I don't care about
- IBIS
- Single card slot
- No functional grip
- Focus peaking
Can't elaborate on the rest. The other benefits can all be seen on a D850.
810 on top and Z6 on bottom. You can see very clear grey hazy wave patterns.
Second image is from RawDigger, you can see all the individual pixel errors.
Third at 100%, so please don't tell me it's only pixel peeping.
This was 1.0 firmware, I purchased the Z6 used. Not sure about 3.0 which I've just updated the firmware to.