Olympus VG-110 has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features TruePic III processor. On the other hand, Canon ELPH 150 IS has a
20.0MP 1/2.3' (6.17 x 4.55 mm ) sized CCD sensor and features Digic 4+ processor.
Canon ELPH 150 IS's sensor provides 8MP more than Olympus VG-110'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 VG-110 and ELPH 150 IS sensor size comparison.
Olympus VG-110 and Canon ELPH 150 IS 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 Olympus VG-110 has 68% larger pixel area compared to Canon ELPH 150 IS, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.