Both Panasonic ZS3 and Ricoh GXR S10 24-72mm F2.5-4.4 VC have 10.0 MP resolution sensors but Panasonic ZS3's sensor is 1/2.3-inch (6.08 x 4.56 mm ) and Ricoh GXR S10 24-72mm F2.5-4.4 VC's sensor is 1/1.7-inch (7.44 x 5.58 mm ).
Since Ricoh GXR S10 24-72mm F2.5-4.4 VC'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 Panasonic ZS3.
Below you can see the ZS3 and GXR S10 24-72mm F2.5-4.4 VC sensor size comparison.
As seen above, Ricoh GXR S10 24-72mm F2.5-4.4 VC has a 1.5x Larger sensor area than Panasonic ZS3. 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.