Sony WX350 has a 18.0MP 1/2.3" (6.17 x 4.55 mm ) sized BSI-CMOS sensor . On the other hand, Panasonic ZS3 has a 10.0MP 1/2.33" (6.08 x 4.56 mm ) sized CCD sensor . Sony WX350's sensor provides 8MP more than Panasonic ZS3'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 WX350 and ZS3 sensor size comparison.
Sony WX350 and Panasonic ZS3 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.