Canon ELPH 190 IS has a 20.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features DIGIC 4+ processor. On the other hand, Casio EX-G1 has a 12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor .
Canon ELPH 190 IS's sensor provides 8MP more than Casio EX-G1'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 190 IS and EX-G1 sensor size comparison.
Canon ELPH 190 IS and Casio EX-G1 have 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 Casio EX-G1 has 65% larger pixel area (2.34µm2 vs 1.41µm2) compared to Canon ELPH 190 IS, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.