Both Canon SD960 IS and Canon G16 have 12.0 MP resolution sensors but Canon SD960 IS's sensor is 1/2.3-inch (6.17 x 4.55 mm ) and Canon G16's sensor is 1/1.7-inch (7.44 x 5.58 mm ).
Since Canon G16'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 SD960 IS.
Below you can see the SD960 IS and G16 sensor size comparison.
Sensor Size and Resolution Comparison image of Canon SD960 IS and Canon G16 Cameras
As seen above, Canon G16 has a 1.5x Larger sensor area than Canon SD960 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.