in French is indeed strictly male. For girls it is always Noelle
In French both are pronounced exactly the same way and for completely correct use it has to have the dots above the "e" (which actually forces the accent on the "-el" instead of "Nol")
But since in some foreign countries, depending on the laws, people don't care that much about the original usage and pronunciation, it's a matter of personal preferences and interest =)
But if you want to avoid the english "No'ul" pronunciation "Noelle
" would be the better choice I think.