Photo Above Data [NIKON Z 6, Sigma 24.0-105.0 mm f/4.0 ART, ISO 16000, ƒ/6.3, 1/200, Focal Length = 95]
I have owned the Fuji X-E series cameras a few years. I love them. Then I bought the Nikon Z6 to be able to shoot mirrorless with some of my Nikon glass.
I think the Fuji X-E3 compares pretty good to the Nikon Z6. I like that the Fuji X-E3 when you are close to someone will not only find their face but their eyes as well.
Now the Nikon Z6 camera automatically detects the subject and selects the focus area. At default settings, the camera gives priority to portrait subjects; if a portrait subject is detected, the selected subject will be indicated by a yellow border (if multiple faces are detected, you can choose your subject using the multi selector).
Just so I could get some photos to use from the service I left the 55-200mm on the Fuji X-E3 and the 24-105mm on the Nikon Z6.
No question that the larger full-frame sensor on the Nikon Z6 had less noise. However I was pretty happy with the noise on the Fuji X-E3 as well.
I think that the dynamic range is better with the Nikon Z6. You can see some of that comparison here.
I love the smaller size and weight of the Fuji system. I think the quality is excellent.
I do think that the quality of the images and higher ISO is definitely in favor of the Nikon Z6.