YI M1 has a
20.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor . On the other hand, Nikon 1 J4 has a
18.0MP 1' (13.2 x 8.8 mm ) sized CMOS sensor and features Expeed 4 processor.
Below you can see the M1 and 1 J4 sensor size comparison.
As seen above, YI M1 has a 1.9x Larger sensor area than Nikon 1 J4. 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.