Canon G3 X has a 20.0MP 1" (13.2 x 8.8 mm ) sized BSI-CMOS sensor and features DIGIC 6 processor. On the other hand, Sony A7 has a 24.0MP Full frame (35.8 x 23.9 mm ) sized CMOS sensor and features Bionz X processor.
Below you can see the G3 X and A7 sensor size comparison.
As seen above, Sony A7 has a 7.4x Larger sensor area than Canon G3 X. 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.