Olympus VG-120 has a 14.0MP 1/2.3" (6.17 x 4.55 mm ) sized CCD sensor and features TruePic III processor. On the other hand, Panasonic ZS80 has a 20.0MP 1/2.3" (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features Venus Engine processor.
Panasonic ZS80's sensor provides 6MP more than Olympus VG-120'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 VG-120 and ZS80 sensor size comparison.
Olympus VG-120 and Panasonic ZS80 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 Olympus VG-120 has 46% larger pixel area compared to Panasonic ZS80, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.