ΔE 9.4, close: similar, with a visible difference side by side. USAF Brown is a little lighter, more muted than Sylvaneth Bark.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). USAF Brown is a little lighter, more muted than Sylvaneth Bark.
The same difference applies the other way round: Sylvaneth Bark 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 Sylvaneth Bark on the colour wheel See USAF Brown on the colour wheel
All matches: Sylvaneth Bark equivalents · USAF Brown equivalents