Samsung ST90 has a
14.0MP 1/2.3-inch (6.16 x 4.62 mm ) sized CCD sensor . On the other hand, Canon S95 has a
10.0MP 1/1.7-inch (7.44 x 5.58 mm ) sized CCD sensor and features Digic 4 processor.
Below you can see the ST90 and S95 sensor size comparison.
As seen above, Canon S95 has a 1.5x Larger sensor area than Samsung ST90. 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.