Both Canon SX620 HS and Panasonic LX10 have 20.0 MP resolution sensors but Canon SX620 HS's sensor is 1/2.3" (6.17 x 4.55 mm) ) and Panasonic LX10's sensor is 1″ (13.2 x 8.8 mm ).
Since Panasonic LX10'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 SX620 HS.
Below you can see the SX620 HS and LX10 sensor size comparison.
As seen above, Panasonic LX10 has a 4.1x Larger sensor area than Canon SX620 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.