Both Nikon L31 and Nikon S8200 have 16.0 MP resolution sensors but Nikon L31's sensor is 1/2.3' (6.17 x 4.55 mm ) and Nikon S8200's sensor is 1/2.3-inch (6.17 x 4.55 mm ).
Since Nikon S8200'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 Nikon L31.
Below you can see the L31 and S8200 sensor size comparison.
Sensor Size and Resolution Comparison image of Nikon L31 and Nikon S8200 Cameras
Nikon L31 and Nikon S8200 have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture.