Both Nikon S70 and Fujifilm XQ2 have 12.0 MP resolution sensors but Nikon S70's sensor is 1/2.3-inch (6.17 x 4.55 mm ) and Fujifilm XQ2's sensor is 2/3' (8.8 x 6.6 mm ).
Since Fujifilm XQ2'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 S70.
Below you can see the S70 and XQ2 sensor size comparison.
As seen above, Fujifilm XQ2 has a 2.1x Larger sensor area than Nikon S70. 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.