ΔE 3.8, very close: most people won’t see a difference side by side. Grim Black is a little darker than Smoke Black. They are different kinds of paint: AK Interactive Smoke Black is an opaque base/layer paint and Army Painter Grim Black is a one-coat contrast-style paint, so they won’t behave the same on the model even where the colour is close.
Yes, for most jobs. Very close match (ΔE 4). Grim Black is a little darker than Smoke Black. They are different kinds of paint.
The same difference applies the other way round: Smoke Black is a little lighter.
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 Smoke Black on the colour wheel See Grim Black on the colour wheel
All matches: Smoke Black equivalents · Grim Black equivalents