Casio EX-FC100 has a 9.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CMOS sensor . On the other hand, Ricoh WG-20 has a 14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor .
Ricoh WG-20's sensor provides 5MP more than Casio EX-FC100'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 EX-FC100 and WG-20 sensor size comparison.
Casio EX-FC100 and Ricoh WG-20 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 Casio EX-FC100 has 53% larger pixel area compared to Ricoh WG-20, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.