Both Sony RX1 and Canon G1 X III have 24.0 MP resolution sensors but Sony RX1's sensor is Full frame (35.8 x 23.8 mm ) and Canon G1 X III's sensor is APS-C (22.3 x 14.9 mm ).
Since Sony RX1'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 G1 X III.
Below you can see the RX1 and G1 X III sensor size comparison.
As seen above, Sony RX1 has a 2.6x Larger sensor area than Canon G1 X III. 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.