ΔE 17.9, loose: different enough that you should pick on purpose. Sapphire Blue is a little lighter, cooler than Prism Power.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Sapphire Blue is a little lighter, cooler than Prism Power.
The same difference applies the other way round: Prism Power is a little 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 Prism Power on the colour wheel See Sapphire Blue on the colour wheel
All matches: Prism Power equivalents · Sapphire Blue equivalents