Which dress is nicer for a wedding?

I think the second one. I know I am going against popular opinion here, but the first one seems too racy for a wedding. the second one seems very clic (screams audrey hepburn in my head) and would not go out of style in case you wanted to wear it during a subsequent pregnancy. It is a bit more modest, but also more feminine with the three quarter sleeves and the y silhouette. I also think it sort of de-emphasizes the belly, but that is neither good nor bad, it just depends on how you feel your best. Some women prefer it not to be as noticeable when they are pregnant and some love to show off the bump!