Canon G5 X has a 20.0MP 1-inch (13.2 x 8.8 mm ) sized BSI-CMOS sensor and features DIGIC 6 processor. On the other hand, Canon XC10 has a 12.0MP 1-inch (12.8 x 9.6 mm ) sized CMOS sensor and features DIGIC DV5 processor.
Canon G5 X's sensor provides 8MP more than Canon XC10's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the G5 X and XC10 sensor size comparison.
Canon G5 X and Canon XC10 have almost the same sensor size so none of them has any significant advantage over other in providing control over depth of field when used with same focal length and aperture.