Canon S90 has a
10.0MP 1/1.7-inch (7.44 x 5.58 mm ) sized CCD sensor and features Digic 4 processor. On the other hand, Olympus XZ-10 has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor .
Below you can see the S90 and XZ-10 sensor size comparison.
As seen above, Canon S90 has a 1.5x Larger sensor area than Olympus XZ-10. 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.