Canon 5DS has a 51.0MP Full frame (36 x 24 mm ) sized CMOS sensor and features Dual DIGIC 6 processor. On the other hand, Panasonic S5 II has a 24.0MP Full frame (35.6 x 23.8 mm ) sized CMOS sensor and features Venus Engine processor.
Canon 5DS's sensor provides 27MP more than Panasonic S5 II'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.
One other difference between these two cameras that is worth mentioning is that Panasonic S5 II'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 5DS and S5 Mark II sensor size comparison.
Sensor Size and Resolution Comparison image of Canon 5DS and Panasonic S5 II Cameras
Canon 5DS and Panasonic S5 II have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.