Both YI M1 and Sony a5000 have 20.0 MP resolution sensors but YI M1's sensor is Four Thirds (17.3 x 13 mm ) and Sony a5000's sensor is APS-C (23.2 x 15.4 mm ).
Since Sony a5000'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 YI M1.
Below you can see the M1 and a5000 sensor size comparison.
As seen above, Sony a5000 has a 1.6x Larger sensor area than YI M1. 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.