How to say Merry Christmas in Germany？
What's the different between Frohe Weihnachten and Fröhliche Weihnachten?

Question

Answer

As Jura points out, there is no essential difference.
I have looked up froh and fröhlich in the dictionary, when using the words I found, I would translate

"Frohe Weihnachten" = "Merry Christmas"
"Fröhliche Weihnachten" = "Joyful Christmas"

which again, is more or less the same on my mind

Answer

There is no difference  between Frohe Weihnachten and Fröhliche Weihnachten , either is acceptable.