I'd say Ju-li-ET although to be honest, it's more like JU-li-ET, with equal stress on the first and last syllable. First syllable only sounds wrong. I'm from England.
Juliet and
Juliette are exactly the same.
I prefer
Juliet to
Juliette. It is a bit tragic really but pretty. I wouldn't use it but I'd consider it as a middle name.