Black Brown vs Abaddon Black

How close are they?

ΔE 16.0, loose: different enough that you should pick on purpose. Abaddon Black is a little darker, much more muted than Black Brown.

Can I use Abaddon Black instead of Black Brown?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Abaddon Black is a little darker, much more muted than Black Brown.

Can I use Black Brown instead of Abaddon Black?

The same difference applies the other way round: Black Brown is a little lighter, much 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.