ΔE 9.2, close: similar, with a visible difference side by side. Flat Brown is a little lighter, more muted than Schokobraun RAL 8017.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Flat Brown is a little lighter, more muted than Schokobraun RAL 8017.
The same difference applies the other way round: Schokobraun RAL 8017 is a little darker, more saturated.
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 Schokobraun RAL 8017 on the colour wheel See Flat Brown on the colour wheel
All matches: Schokobraun RAL 8017 equivalents · Flat Brown equivalents