YI M1 has a
20.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor . On the other hand, Sony A7c has a
24.0MP Full frame (35.8 x 23.8 mm ) sized BSI-CMOS sensor and features Bionz X processor.
Below you can see the M1 and A7c sensor size comparison.
As seen above, Sony A7c has a 3.8x 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.