Sony A1 has a
50.0MP Full frame (35.9 x 24 mm ) sized Stacked CMOS sensor and features Dual Bionz XR processor. On the other hand, Pentax K-1 II has a
36.0MP Full frame (35.9 x 24 mm ) sized CMOS sensor and features PRIME IV processor.
Sony A1's sensor provides 14MP more than Pentax K-1 II'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.
One other difference between these two cameras that is worth mentioning is that Pentax K-1 II'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 moiré occurring in certain scenes.
Below you can see the A1 and K-1 Mark II sensor size comparison.
Sony A1 and Pentax K-1 II have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Pentax K-1 II has 37% larger pixel area (23.83µm2 vs 17.31µm2) compared to Sony A1, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.