What the texts say. With eudokia (nominative), the hymn has three phrases: glory to God in the highest, on earth peace, among men good will. With eudokias (genitive, one added letter), it has two: glory to God in the highest, and on earth peace among men of good pleasure, that is, people on whom God’s favour rests. The Latin Vulgate follows the second form: pax hominibus bonae voluntatis, “peace to men of good will.”
The manuscript evidence. The genitive is read by the first hands of Codex Sinaiticus and Codex Vaticanus, by Codex Alexandrinus, Codex Bezae and Codex Washingtonianus, and by most Old Latin witnesses. The nominative is read by later correctors of Sinaiticus and Vaticanus, by most later Greek manuscripts and the Byzantine tradition, and by Syriac and Bohairic Coptic witnesses. The NET Bible, like Nestle’s critical text, adopts the genitive as better attested in the oldest witnesses and as the harder reading (Strong, though the nominative has far more manuscripts).
What the Orthodox Church reads and sings. The Patriarchal Text reads eudokia, and so does the Church’s Great Doxology, sung at Matins on Sundays and feasts, which opens with the angels’ hymn in the Byzantine form. Orthodox Christians thus sing “good will toward men” every week.
How translations handle it. The KJV, NKJV and Reina-Valera 1909 follow the nominative: “good will toward men.” The Douay-Rheims, from the Latin, reads “peace to men of good will.” The ASV, ESV, NIV, NRSVUE and RSV Catholic Edition follow the Greek genitive: peace among those “with whom he is pleased” or “whom he favors,” most with a note on the other reading.
What it does and does not change. A common misunderstanding is that “men of good will” means peace only for people who are already good. In the New Testament eudokia often describes God’s own good pleasure (Matthew 11:26; Ephesians 1:5), and the genitive is best read as peace for those whom God favours. Read either way, the angels announce peace as God’s gift in the birth of Christ, not as a reward for human merit. The difference is one of emphasis, not of doctrine.