Just want to speculate on which one you would use for the Best IQ for Portraits, Travel and landscapes and social events.
Best? The Nikon will be far more versatile, giving you access to a much larger selection of lenses, flash, and accessories. Image quality will be superior in many situations, and getting the best results from raw files is easier. Shooting moving subjects with continuous autofocus will be faster and more accurate.
The Fuji system has fewer lenses available, especially long fast telephotos, though the basics are well covered and many of the lenses are simply fantastic. Flash is still an issue with the Fuji system, as is continuous AF.
All that said, I shoot about 90% of my work assignments and 100% of my personal work with a Fuji kit. The image quality of the Fuji is more than good enough for portraits, travel, and social events (and shooting events with fast primes and no flash makes me very happy). Landscapes are a bit trickier with the X-Trans Fuji sensor, but I have been getting good results.
In my experience I prefer shooting the Fuji with the smaller primes, and I can get a Fuji kit that covers a wide range of situations into a very small and light bag. This can be a significant advantage for travel, or even everyday work. But I do have the larger zooms and they are quite good. I don't feel at all constrained by the Fuji system unless I need to shoot a sports assignment or I need especially high resolution in one shot.