ΔE 22.8, loose: different enough that you should pick on purpose. Sunny Yellow is noticeably lighter, cooler than Phalanx Yellow.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Sunny Yellow is noticeably lighter, cooler than Phalanx Yellow.
The same difference applies the other way round: Phalanx Yellow is noticeably darker, 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 Phalanx Yellow on the colour wheel See Sunny Yellow on the colour wheel
All matches: Phalanx Yellow equivalents · Sunny Yellow equivalents