I have both the D750 and D500. For wildlife and when the extra reach is needed, I choose the D500 first. For everything else, I go with the D750. Both are excellent, and both have their advantages. The low light capabilities of the D750 are a little better than the D500 - but it definitely isn't a huge difference by any means. High ISO's (noise) are closer to the D610 than the D7200 from my own experience.
The only thing I don't care for about the D500 is its layout. All my other Nikon DSLR bodies have used a similar layout to the D750. The D500 doesn't have U1 or U2 which I always programmed or even a mode button to change between Aperture Priority, Shutter Priority, or Manual Mode. The U1 and U2 program modes allowed me to quickly switch between two very different settings (Aperture Priority with AF-S and shutter button for focusing while U2 is set for Manual Mode with BBF and AF-C with Auto-ISO).
One advantage of the D500 over the D750 is it has the AF Fine Tune. It can automatically calibrate lenses. The D750 requires the user to input a calibration value after determining the AF based on results of visually eyeballing images.
Here's a sample from yesterday with my D500, 300mm f/4 PF, and 1.4x TC.
EDIT: and of course now I see a spot on my sensor that I missed during editing. :beguiled: