Each of the Christmas Gospels gives us a different perspective on Christmas. Together, they give us the whole story of Christmas.
The Gospels for Christmas Eve and Midnight Mass focus on the people and details of the Christmas story. Mary and Joseph, angels and shepherds, etc. The readings are very human and very intimate.
The readings for Christmas are different. They step back from the intimacy of the earlier readings, and give us the big picture of Christmas. The first reading (Isaiah) tells about God intervening, acting directly to comfort his people and to restore them.
The Gospel for Christmas (John) shows Jesus fulfilling what Isaiah foretold. That the child born to poor travelers is none other than the eternal Word. And that God with us is one of us.