ΔE 15.7, loose: different enough that you should pick on purpose. Pyrrole Red is much more saturated than Astorath Red.
Can I use Pyrrole Red instead of Astorath Red?
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Pyrrole Red is much more saturated than Astorath Red.
Can I use Astorath Red instead of Pyrrole Red?
The same difference applies the other way round: Astorath Red is much more muted.
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.