Both Sony W220 and Pentax MX-1 have 12.0 MP resolution sensors but Sony W220'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 Sony W220.
Below you can see the W220 and MX-1 sensor size comparison.
As seen above, Pentax MX-1 has a 1.5x Larger sensor area than Sony W220. 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.