Since I am not an ornithologist, I don't know the difference between a raven and a crow and I am not able to tell the two species apart.
However I have noticed that in most parts of Germany these birds are completely black, but in Potsdam they have grey backs.
In Ireland they are bigger than in Germany and they have yellow beaks. I have also noticed that in Northern Europe birds like sparrows or doves or blackbirds are bigger than their counterparts in Southern Europe.
The above are simple observations of a layman.