Both Samsung NX500 and Samsung NX1 have 28.0 MP resolution sensors but Samsung NX500's sensor is APS-C (23.5 x 15.7 mm ) and Samsung NX1's sensor is APS-C (23.5 x 15.7 mm ).
Since Samsung NX1'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 Samsung NX500.
Another similarity between these two cameras is that both Samsung NX1 and Samsung NX500 sensors lack anti-alias (Low-Pass) filters. 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 NX500 and NX1 sensor size comparison.
Samsung NX500 and Samsung NX1 sensors have exactly the same size so none of them has any advantage over other in this area.