Olympus VR-330 has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features TruePic III processor. On the other hand, Canon SX170 IS has a
16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Digic 4 processor.
Below you can see the VR-330 and SX170 IS sensor size comparison.
Olympus VR-330 and Canon SX170 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 VR-330 has 15% larger pixel area compared to Canon SX170 IS, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.