ΔE 17.3, loose: different enough that you should pick on purpose. Silver is noticeably darker than Steel.
✓ AMMO ATOM user guide chart lists these two as equivalents.
Can I use Silver instead of Steel?
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Silver is noticeably darker than Steel.
Can I use Steel instead of Silver?
The same difference applies the other way round: Steel is noticeably lighter.
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.