IF I were already invested in Nikon DX gear and lenses, the answer is obvious: The 500 benefits from a lot of D5 tech, and since I already had some DX Nikkor glass, I would not see enough difference to an XT2, personally, to prompt me to chuck all that and convert to a Fujifilm system (and investment).
However . . . . .
IF I were starting from scratch, I'd way prefer the XT2 for the film sims and a far superior lens inventory over the D500. I, like many others, have the impression that Nikon has not developed serious glass for their DX products, and the available range does not compare with the Fujifilm offerings across the board. I would not be inclined to buy the serious FX glass to use with their DX offerings, though some do.
Fujifilm had the remarkable advantage of offering a lens range that has no legacy of having to work with film or film bodies, and are actually a 'system' of lenses that are part optical and part software corrected in-camera: This is why their lens tests are remarkably free of most lens aberration gremlins. Plus these lenses work on 'DSLR-esque' bodies (XT's), 'rangefinder-ish' bodies (XP's), and your basic 'digital brick' shaped bodies (led off by the XE's) which is a remarkable facility unmatched by any other system.
For me, adding the grip is no problem, I'll gladly take the increased size/weight to gain the facility of having THREE batteries online, I have bigger hands, so it's no concern there.
Nikon makes some of the greatest cameras in the world, lenses as well. But I am not of the opinion that they have done all they could to treat their DX users as well as their FX users when it comes to glass, and lenses are the only true investment: Bodies will come and go as technology marches on and improves at a dizzying rate, but not having glass that you can accumulate and value over time would tilt this to Fujifilm for me. Nikon has just treated their DX lens offerings in general as a range of 'kit lenses'.