ΔE 25.0, loose: different enough that you should pick on purpose. Radiant Yellow is a little darker, much more muted than Pearl Yellow. They are different kinds of paint: Tamiya Pearl Yellow is a pearl paint and Vallejo Radiant Yellow is a metallic, so they won’t behave the same on the model even where the colour is close.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 25). Radiant Yellow is a little darker, much more muted than Pearl Yellow. They are different kinds of paint.
The same difference applies the other way round: Pearl Yellow is a little lighter, much more saturated.
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 Pearl Yellow on the colour wheel See Radiant Yellow on the colour wheel
All matches: Pearl Yellow equivalents · Radiant Yellow equivalents