Both Olympus 1s and Leica V-Lux 4 have 12.0 MP resolution sensors but Olympus 1s's sensor is 1/1.7' (7.44 x 5.58 mm ) and Leica V-Lux 4's sensor is 1/2.3-inch (6.08 x 4.56 mm ).
Since Olympus 1s'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 V-Lux 4.
Below you can see the 1s and V-Lux 4 sensor size comparison.
As seen above, Olympus 1s has a 1.5x Larger sensor area than Leica V-Lux 4. 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.