Both Panasonic ZS3 and Nikon S30 have 10.0 MP resolution sensors but Panasonic ZS3's sensor is 1/2.3-inch (6.08 x 4.56 mm ) and Nikon S30's sensor is 1/3-inch (4.8 x 3.6 mm ).
Since Panasonic ZS3'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 Nikon S30.
Below you can see the ZS3 and S30 sensor size comparison.
As seen above, Panasonic ZS3 has a 1.6x Larger sensor area than Nikon S30. 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.