Both Nikon P7100 and Fujifilm S8100fd have 10.0 MP resolution sensors but Nikon P7100's sensor is 1/1.7-inch (7.44 x 5.58 mm ) and Fujifilm S8100fd's sensor is 1/2.3-inch (6.17 x 4.55 mm ).
Since Nikon P7100'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 S8100fd.
Below you can see the P7100 and S8100fd sensor size comparison.
As seen above, Nikon P7100 has a 1.5x Larger sensor area than Fujifilm S8100fd. 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.