Both Fujifilm X-Pro1 and Panasonic GX85 have 16.0 MP resolution sensors but Fujifilm X-Pro1's sensor is APS-C (23.6 x 15.6 mm ) and Panasonic GX85's sensor is Four Thirds (17.3 x 13 mm ).
Since Fujifilm X-Pro1'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 GX85.
Another similarity between these two cameras is that both Panasonic GX85 and Fujifilm X-Pro1 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 X-Pro1 and GX85 sensor size comparison.
As seen above, Fujifilm X-Pro1 has a 1.6x Larger sensor area than Panasonic GX85. 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.