Canon SX200 IS has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Canon SX600 HS has a
16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features DIGIC 4+ processor.
Below you can see the SX200 IS and SX600 HS sensor size comparison.
Canon SX200 IS and Canon SX600 HS 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 SX200 IS has 32% larger pixel area compared to Canon SX600 HS, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.