Both Fujifilm S9400W and Pentax K-500 have 16.0 MP resolution sensors but Fujifilm S9400W's sensor is 1/2.3-inch (6.17 x 4.55 mm ) and Pentax K-500's sensor is APS-C (23.7 x 15.7 mm ).
Since Pentax K-500's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Fujifilm S9400W.
Below you can see the S9400W and K-500 sensor size comparison.
As seen above, Pentax K-500 has a 13.3x Larger sensor area than Fujifilm S9400W. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.