This is just a quick comparison shooting some ornaments on my tree. First this is using my Sigma 35mm F1.4 ART DG HSM on the Nikon Z6 using the FTZ Mount Adapter.
With the Fuji I am using the kit lens XF 18-55mm ƒ/2.8-4. It is close to the same format when I shot it to compare to the 35mm.
Here I am shooting with telephoto range using the Nikon 85mm.
Here I cropped in to about 100%
Overall I think the Nikon Z6 focused faster. I was using the point to focus. I did the same thing with the Fuji X-E3 but there is a little back and forth with the Fuji.
The larger sensor gave a cleaner file and less noise with the Nikon Z6 in my opinion.
What I did notice is that the Fuji kit lens compares nicely to the two sharpest lenses I own for the Nikons.
When it comes to travel I still would prefer to carry the smaller Fuji. I think I give up a little performance to pick it, but less weight.
When it comes to performance I believe the Nikon wins.