Canon A3500 IS has a
16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features DIGIC 4 processor. On the other hand, Olympus SP-565UZ has a
10.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor .
Canon A3500 IS's sensor provides 6MP more than Olympus SP-565UZ'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 A3500 IS and SP-565UZ sensor size comparison.
Canon A3500 IS and Olympus SP-565UZ 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.