Samsung GX-20 has a 15.0MP APS-C (23.4 x 15.6 mm ) sized CMOS sensor . On the other hand, Samsung GX-10 has a 10.0MP APS-C (23.5 x 15.7 mm ) sized CCD sensor .
Samsung GX-20's sensor provides 5MP more than Samsung GX-10'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 GX-20 and GX-10 sensor size comparison.
Samsung GX-20 and Samsung GX-10 have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.