Both Canon G9 X and Canon SX610 HS have 20.0 MP resolution sensors but Canon G9 X's sensor is 1″ (13.2 x 8.8 mm ) and Canon SX610 HS's sensor is 1/2.3' (6.17 x 4.55 mm ).
Since Canon G9 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 Canon SX610 HS.
Below you can see the G9 X and SX610 HS sensor size comparison.
As seen above, Canon G9 X has a 4.1x Larger sensor area than Canon SX610 HS. 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.