Olympus VH-515 has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features TruePic III+ processor. On the other hand, Panasonic ZS70 has a
20.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features Venus Engine processor.
Panasonic ZS70's sensor provides 8MP more than Olympus VH-515'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 VH-515 and ZS70 sensor size comparison.
Sensor Size and Resolution Comparison image of Olympus VH-515 and Panasonic ZS70 Cameras
Olympus VH-515 and Panasonic ZS70 have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture.
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Olympus VH-515
or the
Panasonic ZS70 ,
including hyperfocal distance.