I do prefer Vivian over Vivien, probably because it was the only spelling I knew growing up. I pronounce the last syllable closer to "un" than "en", though. The Vivien spelling always looks a bit odd to me, but I don't mind it. Makes sense if "en" is the desired sound. I stress the first syllable for both of these.
Vivienne is very nice, but I stress the last syllable when I say it and tend to prefer it as a middle name.