Both Canon G5 X and Panasonic LZ40 have 20.0 MP resolution sensors but Canon G5 X's sensor is 1-inch (13.2 x 8.8 mm ) and Panasonic LZ40's sensor is 1/2.3-inch (6.17 x 4.55 mm ).
Since Canon G5 X'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 LZ40.
Below you can see the G5 X and LZ40 sensor size comparison.
As seen above, Canon G5 X has a 4.1x Larger sensor area than Panasonic LZ40. 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.