Both Casio EX-100 and Canon ELPH 310 HS have 12.0 MP resolution sensors but Casio EX-100's sensor is 1/1.7-inch (7.44 x 5.58 mm ) and Canon ELPH 310 HS's sensor is 1/2.3-inch (6.17 x 4.55 mm ).
Since Casio EX-100'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 Canon ELPH 310 HS.
Below you can see the EX-100 and ELPH 310 HS sensor size comparison.
As seen above, Casio EX-100 has a 1.5x Larger sensor area than Canon ELPH 310 HS. 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.