I've always thought
Marian was pretty, too. It does have this really deep, mature quality to it, and it's velvety and deep red and black. It's very sensual. I only like that spelling when on a girl.
Marion I think looks more masculine, so that's the spelling I consider to be the boy version. I like it on a boy, too.
I think people would spell it
Marian. That's by far more common I think.