Tirstin, I concur with your findings but your first point In the negative section. I think the files of both cameras are pretty close in that regard. If anything, they look sharper on the Z6 but in can be because auto and manual focus are almost always spot on at any aperture. I haven't notice anymore noise in the shadows and, like you, often work with dark images in high iso for stage.
Sample variation doesn't sound likely in sensor? I'm currently using light room almost exclusively, may have an impact?
I will post a review with examples soon. I used the Z6 for a month in Poland and ended up going back to HDR bracketing to avoid the Z6's banded shadow noise. The noise I can deal with, but the banding has ruined images for me. I had gotten used to highlight-weighted single shot HDR shooting with the D750, and quickly found out that doesn't fly with the Z6.
The sharpness I honestly don't have an issue with, it's not a big deal. I forget about it until I open a D750 raw and see the difference.
