Both Canon SX200 IS and Casio EX-10 have 12.0 MP resolution sensors but Canon SX200 IS's sensor is 1/2.3-inch (6.17 x 4.55 mm ) and Casio EX-10's sensor is 1/1.7-inch (7.44 x 5.58 mm ).
Since Casio EX-10's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Canon SX200 IS.
Below you can see the SX200 IS and EX-10 sensor size comparison.
As seen above, Casio EX-10 has a 1.5x Larger sensor area than Canon SX200 IS. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.