1. I definitely prefer
Susanna because it's closest to the original, Sousanna, and because that h just seems unnecessary (sort of like an attempt to make it more Biblical looking rather than just a Greek form of a Biblical name, i.e.,
Hannah,
Shoshannah,
Deborah,
Keturah,
Rebekah,
Sarah,
Leah).
Susanna looks more streamlined and lovely to these eyes.
2. I've considered this point myself because I adore
Susanna, however, I've come to the conclusion that even if it does to some, it's no biggie.
Susanna refers to a song not to someone notorious. I don't think children or even young adults would be overly concerned with the association.
3. I like
Susanna much better than
Olivia not only because it's less common but because I just prefer the sound of it better.
BTW, I read once that
Susannah has traditionally been the more common spelling in the UK while
Susanna as been the more common spelling in the US.