I would only use
Margaret with a nickname. I adore
Maggie and would use it just for that. (Well and that it would honor my grandmother). I also like
Meg and
Greta.
I kind of like
Margaret. It feels very old and dated and heavy. A nickname keeps it young and fresh. I actually like
Marguerite better.
Maggie is a top contender for a second daughter (if we have one) and I would strongly consider both
Margaret and
Marguerite. I like
Marguerite more but worry about people having difficulty spelling/pronouncing it. And I think most people find it more dated than
Margaret.