Both Panasonic FX75 and Nikon 1 J3 have 14.0 MP resolution sensors but Panasonic FX75's sensor is 1/2.3-inch (6.08 x 4.56 mm ) and Nikon 1 J3's sensor is 1-inch (13.2 x 8.8 mm ).
Since Nikon 1 J3'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 Panasonic FX75.
Below you can see the FX75 and 1 J3 sensor size comparison.
As seen above, Nikon 1 J3 has a 4.2x Larger sensor area than Panasonic FX75. 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.