Fujifilm S9900w has a 16.0MP (1/2. ) sized CMOS sensor . On the other hand, Pentax E90 has a 10.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor and features Prime processor.
Fujifilm S9900w's sensor provides 6MP more than Pentax E90'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 S9900w and E90 sensor size comparison.
As seen above, Pentax E90 has a infx Larger sensor area than Fujifilm S9900w. 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.