The D500 and D7500 share the same sensor and processor so, from strictly an image quality standpoint, they should be indistinguishable. The D7500 has the same autofocus system as the D750 so, if you're pleased with that camera's AF, you should be at least as happy with the D7500 and perhaps a bit more so due to the wider coverage of the DX sensor. Do you like the User 1 and User 2 modes of the D750? If so, you may find the D7500 more familiar as it has the same interface.
Personally, I chose the D500 for its flagship autofocus system, best-in-class burst rate and buffer and a few other reasons. The D500 can be used with a battery grip, which is important to me. While I typically shoot in landscape orientation, I use portrait orientation with enough frequency to make that of real value to me. Also, the dedicated AF-ON button and thumbstick are nice features. I'm a dedicated back-button focus shooter. I use the thumbstick with great frequency; often when I'm in the midst of photographing a bird or land animal.
The D500 eyepiece also delivers a more magnified view of the composition. It needs less light to focus. The rear LCD displays a higher resolution image, which makes review and evaluation of photos a bit easier. And the build quality is better. To be fair, however, I'm an infrequent traveler to rugged, remote locales. In other words, I'm not that hard on my gear.
Returning to the subject of User modes, I have to say this was probably the biggest adjustment for me, as someone who'd been using a D600/610 for wildlife photography before upgrading to the D500. I loved the User modes and it took some time to become comfortable with the Banks in the pro body. I still prefer User modes to Banks but also find I'm almost exclusively in full manual, which largely negates any benefits of one over the other.
So, from strictly a performance standpoint, both bodies can be used to make great images. I would argue the D500 has the edge in several significant categories. I also think the D500 offers clear advantages in user interface...with one caveat. If you like the User modes, don't particularly care to shoot with a grip or prefer something a bit smaller & lighter, I'd recommend the D7500.
Otherwise, if your budget allows and you want the best performance, get the D500.