Canon 7D MII has a
20.0MP APS-C (22.4 x 15 mm ) sized CMOS sensor and features DIGIC 6 (dual) processor. On the other hand, Pentax ist DS2 has a
6.0MP APS-C (23.5 x 15.7 mm ) sized CCD sensor .
Canon 7D MII's sensor provides 14MP more than Pentax ist DS2's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the 7D MII and ist DS2 sensor size comparison.
Canon 7D MII and Pentax ist DS2 have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.