Sieve extprograms socket vs. direct execution

[E.B.]

Hi, I'm hoping to get some clarification of the differences between calling
a script using the Sieve extprograms plugin execute method via direct
execution or using the socket feature.

Being naive, I see the socket option and think that way you tell Dovecot
to spawn a daemon and I think that's going to be far superior in performance.
But if that really was the difference, why would direct execution even be
an option?  (And doesn't the daemon still have to spawn a new shell every
time if the target is a shell script?  Does that defeat the purpose of having
a daemon?)

So I don't really know what the difference is, and under what circumstances
you'd want to use one or the other.

Can someone please help clarify?