Leica SL has a 24.0MP Full frame (36 x 24 mm ) sized CMOS sensor and features Maestro II processor. On the other hand, Nikon D5 has a 21.0MP Full frame (35.8 x 23.9 mm ) sized CMOS sensor and features Expeed 5 processor.
Another difference between these two cameras is that Leica SL'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 SL and D5 sensor size comparison.
Leica SL and Nikon D5 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.