Both Sony WX50 and Fujifilm X-M1 have 16.0 MP resolution sensors but Sony WX50's sensor is 1/2.3-inch (6.17 x 4.55 mm ) and Fujifilm X-M1's sensor is APS-C (23.6 x 15.6 mm ).
Since Fujifilm X-M1'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 Sony WX50.
One other difference between these two cameras that is worth mentioning is that Fujifilm X-M1'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 WX50 and X-M1 sensor size comparison.
As seen above, Fujifilm X-M1 has a 13.1x Larger sensor area than Sony WX50. 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.