Both Nikon D7100 and Nikon D5600 have 24.0 MP resolution sensors but Nikon D7100's sensor is APS-C (23.5 x 15.6 mm ) and Nikon D5600's sensor is APS-C (23.5 x 15.6 mm ).
Since Nikon D5600'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 D7100.
Another similarity between these two cameras is that both Nikon D5600 and Nikon D7100 sensors lack anti-alias (Low-Pass) filters. 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 D7100 and D5600 sensor size comparison.
Nikon D7100 and Nikon D5600 sensors have exactly the same size so none of them has any advantage over other in this area.