My Italian textbook says that we can use essere with a profession sticking to the following rules: If essere is followed by a noun only (no adjective), you don't use any article, e.g.
Lui è dottore.
If essere is followed by a noun and an adjective, you use an indefinite article, e.g.
Lui è un buon dottore.
I saw a YouTube video where native Italians talk about their jobs. One of them says:
Sono un sacerdote.
It's obvious that you can include or exclude an indefinite article in an Italian phrase stating your profession with essere without an adjective.
My question is this: is any of them more correct than the other or are both equally correct?