At 50 M during day-light hours: A red dot sight is far superior to a scope: Better FOV, quicker target acquisition.
At dawn/dusk, during bad light: Scope.
I have experience with both the Burris Fastfire 11 mini red dot, (On rifles and shotguns) and the Aimpoint Hunter S34 red dot (on rifles): Both perform excellent and hold their zero for years. The newer Burris Fastfire 111 has improved access to the battery compartment.
A 'best of both worlds' set up would be to mount a traditional scope on your rifle, fix a Picatinny rail on top of the scope to mount a min-red dot sight. (Burris, Vortex). Quite common in the States, less often seen in the UK.