Canon D30 has a 12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features DIGIC 4 processor. On the other hand, Ricoh WG-6 has a 20.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor .
Ricoh WG-6's sensor provides 8MP more than Canon D30's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the D30 and WG-6 sensor size comparison.
Canon D30 and Ricoh WG-6 have sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Canon D30 has 68% larger pixel area compared to Ricoh WG-6, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.