ΔE 8.9, close: similar, with a visible difference side by side. Cam. Middle Brown is a little lighter, more saturated, cooler than Burnt Sienna Umber.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Cam. Middle Brown is a little lighter, more saturated, cooler than Burnt Sienna Umber.
The same difference applies the other way round: Burnt Sienna Umber is a little darker, more muted, warmer.
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 Umber on the colour wheel See Cam. Middle Brown on the colour wheel
All matches: Burnt Sienna Umber equivalents · Cam. Middle Brown equivalents