I have used a long line of Nikon cameras, ever since switching from a pro-body Canon (film) to my first digital the Nikon D70, D90, D2 (and some other D2 versions). After that it was a D3 (several versions like the D3Xs), D4, D800, D850, D5 and now the Z9. I am pretty familiar with the menu system from all the previous cameras. Like so many users of the Z9, I find it to be the best all around camera that I've ever used for both stills and (finally) video. Intermittently while using the Nikons, I tried a couple of Canon pro bodies as well. When you are using the high end pro bodies, there's not really that much difference. Some might have an advantage with focus that goes away in time, and others might have better video for a period of time.
The Nikon Z9 has an excellent autofocus system, amazing image quality and very fast performance for sports and action. If I have one small issue, it's that the images seem to have slightly more noise at high ISO settings than my Nikon D5 DSLR, but I find it can be easily corrected with minimal (unnoticeable) loss of quality.