Nikon D5 has a 21.0MP Full frame (35.8 x 23.9 mm ) sized CMOS sensor and features Expeed 5 processor. On the other hand, Sony A7 II has a 24.0MP Full frame (35.8 x 23.9 mm ) sized CMOS sensor and features Bionz X processor.
Another difference between these two cameras is that Nikon D5'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 D5 and A7 II sensor size comparison.
Nikon D5 and Sony A7 II sensors have exactly the same size so none of them has any advantage over other in this area.