ΔE 16.3, loose: different enough that you should pick on purpose. Orange Brown is noticeably lighter, warmer than Burnt Sienna.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Orange Brown is noticeably lighter, warmer than Burnt Sienna.
The same difference applies the other way round: Burnt Sienna is noticeably darker, 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 Burnt Sienna on the colour wheel See Orange Brown on the colour wheel
All matches: Burnt Sienna equivalents · Orange Brown equivalents