Ricoh WG-6 has a 20.0MP 1/2.3" (6.17 x 4.55 mm ) sized BSI-CMOS sensor . On the other hand, Leica M9-P has a 18.0MP Full frame (36 x 24 mm ) sized CCD sensor .
One other difference between these two cameras that is worth mentioning is that Leica M9-P's sensor doesn't have an anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moire occurring in certain scenes.
Below you can see the WG-6 and M9-P sensor size comparison.
As seen above, Leica M9-P has a 30.8x Larger sensor area than Ricoh WG-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.