Pentax K-50 has a 16.0MP APS-C (23.7 x 15.7 mm ) sized CMOS sensor and features PRIME M processor. On the other hand, Fujifilm S1 Pro has a 3.0MP APS-C (23 x 15.5 mm ) sized CCD sensor . Pentax K-50's sensor provides 13MP more than Fujifilm S1 Pro'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 K-50 and S1 Pro sensor size comparison.
Pentax K-50 and Fujifilm S1 Pro 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.