I've been using Nikon kit mostly for many years and most recently the Nikon D850 but i have also recently added a Nikon mirrorless Z7 and dedicated S lenses to my kit and i'm finding that it's very much better for street shooting, travelling or just a combination of both. The Z7 with 24-70 S lens is literally half the weight of the D850 with 24-70 VR and a lot smaller. Image quality is very similar so that's not really a factor though edge sharpness seems to be better on the Z7 with the 24-70 S lens. Image sharpness is more important for fashion images where your models face and eyes may be closer to the edge of the image than it might be for a simple portrait. When i am on location and working somewhere where shooting tethered is not possible i used to struggle when reviewing images for the simple reason i had to put on my glasses and examine the screen on the back of the camera and then put my glasses away and all this maybe in bright sunshine causing the screen to be hard to look at. Now with the Z i can see my image to review in the viewfinder and i can set all settings while looking through the viewfinder. This is considerably helping my workflow and keeping the flow of interaction between myself and my model.
Currently i still prefer using the D850 in the studio as it seems a little better tethered and i can go at least four hours without having to change a battery. Battery consumption on the Z7 seems very good until it's tethered. I need to understand this better but it's early days.