ΔE 24.9, loose: different enough that you should pick on purpose. Deep Magenta is a little lighter, more muted, warmer than Medium Violet.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 25). Deep Magenta is a little lighter, more muted, warmer than Medium Violet.
The same difference applies the other way round: Medium Violet is a little darker, more saturated, cooler.
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 Medium Violet on the colour wheel See Deep Magenta on the colour wheel
All matches: Medium Violet equivalents · Deep Magenta equivalents