Both Canon S200 and Fujifilm A100 have 10.0 MP resolution sensors but Canon S200's sensor is 1/1.7 (7.44 x 5.58 mm ) and Fujifilm A100's sensor is 1/2.3-inch (6.17 x 4.55 mm ).
Since Canon S200'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 Fujifilm A100.
Below you can see the S200 and A100 sensor size comparison.
As seen above, Canon S200 has a 1.5x Larger sensor area than Fujifilm A100. 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.