Sony H20 has a
10.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Casio EX-H30 has a
16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Exilim Engine 5.0 processor.
Casio EX-H30's sensor provides 6MP more than Sony H20'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 H20 and EX-H30 sensor size comparison.
Sony H20 and Casio EX-H30 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 Sony H20 has 59% larger pixel area compared to Casio EX-H30, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.