Fujifilm S9900w has a 16.0MP (1/2. ) sized CMOS sensor . On the other hand, Sony A900 has a 25.0MP Full frame (35.9 x 24 mm ) sized CMOS sensor and features Bionz processor.
Sony A900's sensor provides 9MP more than Fujifilm S9900w'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 A900 sensor size comparison.
Sensor Size and Resolution Comparison image of Fujifilm S9900w and Sony A900 Cameras
As seen above, Sony A900 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.