ΔE 17.2, loose: different enough that you should pick on purpose. Moon Yellow is noticeably darker, more saturated, warmer than Sunny Yellow.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Moon Yellow is noticeably darker, more saturated, warmer than Sunny Yellow.
The same difference applies the other way round: Sunny Yellow is noticeably lighter, more muted, 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 Sunny Yellow on the colour wheel See Moon Yellow on the colour wheel
All matches: Sunny Yellow equivalents · Moon Yellow equivalents