Both Sony RX1R and Fujifilm X-T20 have 24.0 MP resolution sensors but Sony RX1R's sensor is Full frame (35.8 x 23.9 mm ) and Fujifilm X-T20's sensor is APS-C (23.6 x 15.6 mm ).
Since Sony RX1R'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 Fujifilm X-T20.
Another similarity between these two cameras is that both Fujifilm X-T20 and Sony RX1R 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 moiré occurring in certain scenes.
Below you can see the RX1R and X-T20 sensor size comparison.
As seen above, Sony RX1R has a 2.3x Larger sensor area than Fujifilm X-T20. 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.