Both Nikon P610 and Panasonic G85 have 16.0 MP resolution sensors but Nikon P610's sensor is 1/2.3" (6.17 x 4.55 mm ) and Panasonic G85's sensor is Four Thirds (17.3 x 13 mm ).
Since Panasonic G85's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Nikon P610.
Another difference between these two cameras is that Panasonic G85's sensor lacks 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 moire occurring in certain scenes.
Below you can see the P610 and G85 sensor size comparison.
As seen above, Panasonic G85 has a 8.0x Larger sensor area than Nikon P610. 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.