Both Canon M6 and Panasonic S1 have 24.0 MP resolution sensors but Canon M6's sensor is APS-C (22.3 x 14.9 mm ) and Panasonic S1's sensor is Full frame (35.6 x 23.8 mm ).
Since Panasonic S1'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 M6.
Another difference between these two cameras is that Panasonic S1's sensor lacks anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moire occurring in certain scenes.
Below you can see the M6 and S1 sensor size comparison.
As seen above, Panasonic S1 has a 2.5x Larger sensor area than Canon M6. 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.