Panasonic FP8 has a
12.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor and features Venus Engine V processor. On the other hand, Sony H400 has a
20.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Bionz(R) processor.
Sony H400's sensor provides 8MP more than Panasonic FP8'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 FP8 and H400 sensor size comparison.
Panasonic FP8 and Sony H400 have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.