Both Canon G7 X MII and Nikon A900 have 20.0 MP resolution sensors but Canon G7 X MII's sensor is 1″ (13.2 x 8.8 mm ) and Nikon A900's sensor is 1/2.3 (6.17 x 4.55 mm ).
Since Canon G7 X MII'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 A900.
Below you can see the G7 X MII and A900 sensor size comparison.
As seen above, Canon G7 X MII has a 4.1x Larger sensor area than Nikon A900. 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.