Kodak C140 has a
8.0MP 1/2.5-inch (5.744 x 4.308 mm ) sized CCD sensor . On the other hand, Kodak M580 has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor .
Kodak M580's sensor provides 6MP more than Kodak C140'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 C140 and M580 sensor size comparison.
As seen above, Kodak M580 has a 1.1x Larger sensor area than Kodak C140. 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.