Both Nikon D750 and Canon 80D have 24.0 MP resolution sensors but Nikon D750's sensor is Full frame (35.9 x 24 mm ) and Canon 80D's sensor is APS-C (22.5 x 15 mm ).
Since Nikon D750'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 Canon 80D.
Below you can see the D750 and 80D sensor size comparison.
As seen above, Nikon D750 has a 2.6x Larger sensor area than Canon 80D. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.