On a Git server, how does the update hook differ from pre-receive?

Question

Accepted Answer

pre-receive runs once for the whole push, while update runs once per ref and can reject individual branch updates

Answer

update runs on the client and pre-receive on the server

Answer

pre-receive cannot reject pushes, only log them

Answer

update runs after the refs are written, so it can only warn

On a Git server, how does the `update` hook differ from `pre-receive`?