Pentax WS80 has a
10.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Prime processor. On the other hand, Nikon AW120 has a
16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CMOS sensor .
Nikon AW120's sensor provides 6MP more than Pentax WS80'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 WS80 and AW120 sensor size comparison.
Pentax WS80 and Nikon AW120 have the same 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 Pentax WS80 has 59% larger pixel area compared to Nikon AW120, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.