I run both @prosodyim and @ejabberd. IMHO, both are easy to set up and maintain nowadays.
Just make sure that you use the file store for #Prosody (not an #RDBMS) and #PostgreSQL for #Ejabberd (not Mnesia) 🙂
Both have some minor features, that might be not present in the other, though. E.g. "great invitations", which are ATM only present in Prosody (but WiP for Ejabberd).