Considering that this is a spoken expression, I think they are about the same--other natives, feel free to contradict--the only difference being that "the same to you" sounds less rushed and maybe a little more polite:
Fred: Merry Christmas!
Tim: Thank you, and the same to you!
"The same to you" is almost invariably a courteous expression - in reply to an expression of good wishes.
"Same to you" can be a return insult : "get stuffed!" - "same to you". As you can imagine, it is a rather childish rejoinder.