Both Nikon L31 and Fujifilm Z900EXR have 16.0 MP resolution sensors but Nikon L31's sensor is 1/2.3' (6.17 x 4.55 mm ) and Fujifilm Z900EXR's sensor is 1/2-inch (6.4 x 4.8 mm ).
Since Fujifilm Z900EXR'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 Z900EXR sensor size comparison.
Sensor Size and Resolution Comparison image of Nikon L31 and Fujifilm Z900EXR Cameras
Nikon L31 and Fujifilm Z900EXR have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.