FujiFilm F80EXR has a
12.0MP 1/2-inch (6.4 x 4.8 mm ) sized CCD sensor and features EXR processor. On the other hand, Panasonic GX85 has a
16.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor and features Venus Engine processor.
One other difference between these two cameras that is worth mentioning is that Panasonic GX85's sensor doesn't have an anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moiré occurring in certain scenes.
Below you can see the F80EXR and GX85 sensor size comparison.
As seen above, Panasonic GX85 has a 7.3x Larger sensor area than FujiFilm F80EXR. 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.