Both Fujifilm S9900w and Ricoh WG-4 have 16.0 MP resolution sensors but Fujifilm S9900w's sensor is (1/2. ) and Ricoh WG-4's sensor is 1/2.3-inch (6.17 x 4.55 mm ).
Since Ricoh WG-4'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 S9900w.
Below you can see the S9900w and WG-4 sensor size comparison.
As seen above, Ricoh WG-4 has a infx Larger sensor area than Fujifilm S9900w. 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.