ΔE 18.0, loose: different enough that you should pick on purpose. Purple Black is noticeably lighter than Corvus Black.
Can I use Purple Black instead of Corvus Black?
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Purple Black is noticeably lighter than Corvus Black.
Can I use Corvus Black instead of Purple Black?
The same difference applies the other way round: Corvus Black is noticeably darker.
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.