Canon SX160 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, Canon SX210 IS has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Digic 4 processor.
Below you can see the SX160 IS and SX210 IS sensor size comparison.
Canon SX160 IS and Canon SX210 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 Canon SX210 IS has 14% larger pixel area (2.01µm2 vs 1.76µm2) compared to Canon SX160 IS, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.