Ricoh GR Digital III has a
10.0MP 1/1.7-inch (7.44 x 5.58 mm ) sized CCD sensor and features GR engine III processor. On the other hand, Ricoh GR has a
16.0MP APS-C (23.7 x 15.7 mm ) sized CMOS sensor .
Ricoh GR's sensor provides 6MP more than Ricoh GR Digital III'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 GR Digital III and GR sensor size comparison.
As seen above, Ricoh GR has a 9.0x Larger sensor area than Ricoh GR Digital III. 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.