ΔE 7.7, close: similar, with a visible difference side by side. Raven Black is a little lighter than RAL 7021 Dunkelgrau.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Raven Black is a little lighter than RAL 7021 Dunkelgrau.
The same difference applies the other way round: RAL 7021 Dunkelgrau is a little darker.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See RAL 7021 Dunkelgrau on the colour wheel See Raven Black on the colour wheel
All matches: RAL 7021 Dunkelgrau equivalents · Raven Black equivalents