ΔE 19.0, loose: different enough that you should pick on purpose. Middle Brown is noticeably darker, more saturated than Ratskin Flesh.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Middle Brown is noticeably darker, more saturated than Ratskin Flesh.
The same difference applies the other way round: Ratskin Flesh is noticeably lighter, more muted.
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 Ratskin Flesh on the colour wheel See Middle Brown on the colour wheel
All matches: Ratskin Flesh equivalents · Middle Brown equivalents