ΔE 6.4, close: similar, with a visible difference side by side. Off-White is a little darker, more saturated than Art White.
Usually, if you are not matching paint already on the model. Close match (ΔE 6). Off-White is a little darker, more saturated than Art White.
The same difference applies the other way round: Art White is a little lighter, more muted.
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 Art White on the colour wheel See Off-White on the colour wheel
All matches: Art White equivalents · Off-White equivalents