Canon S120 has a 12.0MP 1/1.7" (7.44 x 5.58 mm ) sized BSI-CMOS sensor and features Digic 6 processor. On the other hand, Olympus SP-570 UZ has a 10.0MP 1/2.33" (6.08 x 4.56 mm ) sized CCD sensor .
Below you can see the S120 and SP-570 UZ sensor size comparison.
As seen above, Canon S120 has a 1.5x Larger sensor area than Olympus SP-570 UZ. 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.