Both Sony A100 and Leica D-Lux 6 have 10.0 MP resolution sensors but Sony A100's sensor is APS-C (23.6 x 15.8 mm ) and Leica D-Lux 6's sensor is 1/1.7-inch (7.44 x 5.58 mm ).
Since Sony A100'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 Leica D-Lux 6.
Below you can see the A100 and D-Lux 6 sensor size comparison.
As seen above, Sony A100 has a 9.0x Larger sensor area than Leica D-Lux 6. 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.