ΔE 20.5, loose: different enough that you should pick on purpose. Elf Skin Tone is noticeably lighter, much more muted than Middle Brown.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Elf Skin Tone is noticeably lighter, much more muted than Middle Brown.
The same difference applies the other way round: Middle Brown is noticeably darker, 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.
See Middle Brown on the colour wheel See Elf Skin Tone on the colour wheel
All matches: Middle Brown equivalents · Elf Skin Tone equivalents