Both Canon SD970 IS and Pentax MX-1 have 12.0 MP resolution sensors but Canon SD970 IS's sensor is 1/2.3-inch (6.17 x 4.55 mm ) and Pentax MX-1's sensor is 1/1.7-inch (7.44 x 5.58 mm ).
Since Pentax MX-1'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 SD970 IS.
Below you can see the SD970 IS and MX-1 sensor size comparison.
As seen above, Pentax MX-1 has a 1.5x Larger sensor area than Canon SD970 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.