Pentax KP has a 24.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor and features PRIME IV processor. On the other hand, Nikon D7500 has a 21.0MP APS-C (23.5 x 15.7 mm ) sized CMOS sensor and features Expeed 5 processor.
One other difference between these two cameras that is worth mentioning is that Nikon D7500's sensor doesn't have an anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moire occurring in certain scenes.
Below you can see the KP and D7500 sensor size comparison.
Pentax KP and Nikon D7500 have almost the same sensor size so none of them has any significant advantage over other in providing control over depth of field when used with same focal length and aperture.