Sony S930 has a 10.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Canon G15 has a 12.0MP 1/1.7-inch (7.44 x 5.58 mm ) sized CMOS sensor and features Digic 5 processor.
Below you can see the S930 and G15 sensor size comparison.
As seen above, Canon G15 has a 1.5x Larger sensor area than Sony S930. 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.