Panasonic S5 has a 24.0MP Full frame (35.6 x 23.8 mm ) sized CMOS sensor and features Venus Engine processor. On the other hand, Nikon D810A has a 36.0MP Full frame (35.9 x 24 mm ) sized CMOS sensor and features EXPEED 4 processor.
Nikon D810A's sensor provides 12MP more than Panasonic S5'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.
Another difference between these two cameras is that Panasonic S5'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 S5 and D810A sensor size comparison.
![Panasonic S5 vs Nikon D810A Sensor Size Comparison]()
Sensor Size and Resolution Comparison image of Panasonic S5 and Nikon D810A Cameras
Panasonic S5 and Nikon D810A have almost the same sensor size so none of them has any significant advantage over other in providing control over depth of field when used with same focal length and aperture.