Both Fujifilm F750EXR and Pentax VS20 have 16.0 MP resolution sensors but Fujifilm F750EXR's sensor is 1/2-inch (6.4 x 4.8 mm ) and Pentax VS20's sensor is 1/2.3-inch (6.08 x 4.56 mm ).
Since Fujifilm F750EXR'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 Pentax VS20.
Below you can see the F750EXR and VS20 sensor size comparison.
As seen above, Fujifilm F750EXR has a 1.1x Larger sensor area than Pentax VS20. 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.