Pentax K-S2 has a 20.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor and features PRIME MII processor. On the other hand, Sony A6300 has a 24.0MP APS-C (23.5 x 15.6 mm ) sized CMOS sensor and features BIONZ X processor.
Another difference between these two cameras is that Pentax K-S2's sensor lacks 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 K-S2 and A6300 sensor size comparison.
Pentax K-S2 and Sony A6300 have 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-S2 has 20% larger pixel area compared to Sony A6300, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.