ΔE 28.5, loose: different enough that you should pick on purpose. Martian Orange is noticeably darker, cooler than Fire Giant Orange.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 29). Martian Orange is noticeably darker, cooler than Fire Giant Orange.
The same difference applies the other way round: Fire Giant Orange is noticeably lighter, 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 Fire Giant Orange on the colour wheel See Martian Orange on the colour wheel
All matches: Fire Giant Orange equivalents · Martian Orange equivalents