Sony H300 has a 20.0MP 1/2.3" (6.17 x 4.55 mm ) sized CCD sensor and features Bionz(R) processor. On the other hand, Casio EX-100 has a 12.0MP 1/1.7" (7.44 x 5.58 mm ) sized CMOS sensor . Sony H300's sensor provides 8MP more than Casio EX-100'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 H300 and EX-100 sensor size comparison.
As seen above, Casio EX-100 has a 1.5x Larger sensor area than Sony H300. 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.