What better way to sing such an angelic song that with the voice of an angel? I mean it. Josh Groban's voice is that of an angel, and I would not doubt that the voices of the angelic choir singing praises to the newborn king paled in comparison to his own.
I love his rendition of O Holy Night. I love any song by him. His voice is by far the sexiest one out there...well, for a man.