Both Sony NEX-3 and Canon SX30 IS have 14.0 MP resolution sensors but Sony NEX-3's sensor is APS-C (23.4 x 15.6 mm ) and Canon SX30 IS's sensor is 1/2.3-inch (6.17 x 4.55 mm ).
Since Sony NEX-3'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 SX30 IS.
Below you can see the NEX-3 and SX30 IS sensor size comparison.
As seen above, Sony NEX-3 has a 13.0x Larger sensor area than Canon SX30 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.