To say the phrase, "Teacher has arrived."
It should have an order or a rule to compare A and B.
Generally speaking, dedicated sonkeigo verbs and お～になる sound politer than ～られる.
In my textbook "Japanese Demystified" by Eriko Sato, it says "Another way of creating an honorific verb form is to use the same verb form as the passive form (られる etc.). However, the degree of politeness expressed by this form is lower than that expressed by the honorific form with お...になる..."
I think the politeness oder is shown below;
But, sorry to say, I don't know how I think so.