Both Panasonic FX90 and Casio EX-10 have 12.0 MP resolution sensors but Panasonic FX90's sensor is 1/2.3-inch (6.08 x 4.56 mm ) and Casio EX-10's sensor is 1/1.7-inch (7.44 x 5.58 mm ).
Since Casio EX-10's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Panasonic FX90.
Below you can see the FX90 and EX-10 sensor size comparison.
As seen above, Casio EX-10 has a 1.5x Larger sensor area than Panasonic FX90. 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.