* Efesios: This is the most common and straightforward translation, referring to the people of Ephesus. It's suitable when referring to the inhabitants of the city.
* Carta a los Efesios / Epístola a los Efesios: This translates to "Letter to the Ephesians" or "Epistle to the Ephesians," appropriate when referring to the biblical book.
Therefore, the best translation depends on whether you're talking about the people or the book.