even though I doubt the truth of the initial statement
There are actually
various differences between the two,
including the feathers. Even more importantly, the terms aren't clearly defined; in some areas/languages, "ravens" includes "crows", in others it's the other way around, in yet others, they are separate groups.
Where I live, the ravens (Kolkrabe) are the only ones to be
entirely black, including beak and feet, so telling them apart
is a simple matter of blacklisting.