Both Canon SX120 IS and Ricoh GXR S10 24-72mm have 10.0 MP resolution sensors but Canon SX120 IS's sensor is 1/2.5-inch (5.744 x 4.308 mm ) and Ricoh GXR S10 24-72mm's sensor is 1/1.7-inch (7.44 x 5.58 mm ).
Since Ricoh GXR S10 24-72mm'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 Canon SX120 IS.
Below you can see the SX120 IS and GXR S10 24-72mm F2.5-4.4 VC sensor size comparison.
As seen above, Ricoh GXR S10 24-72mm has a 1.7x Larger sensor area than Canon SX120 IS. 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.