Canon 160 has a
20.0MP 1/2.3' (6.17 x 4.55 mm ) sized CCD sensor and features DIGIC 4+ processor. On the other hand, Sony W310 has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor .
Canon 160's sensor provides 8MP more than Sony W310'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 ELPH 160 and W310 sensor size comparison.
Canon 160 and Sony W310 have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Sony W310 has 65% larger pixel area (2.34µm2 vs 1.41µm2) compared to Canon 160, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.