Both Samsung NX1100 and Panasonic GX9 have 20.0 MP resolution sensors but Samsung NX1100's sensor is APS-C (23.5 x 15.7 mm ) and Panasonic GX9's sensor is Four Thirds (17.3 x 13 mm ).
Since Samsung NX1100'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 GX9.
One other difference between these two cameras that is worth mentioning is that Panasonic GX9's sensor doesn't have an 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 moiré occurring in certain scenes.
Below you can see the NX1100 and GX9 sensor size comparison.
As seen above, Samsung NX1100 has a 1.6x Larger sensor area than Panasonic GX9. 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.