I like
Louisa. I think it sounds more mature than
Ava and
Olivia-- not mature like "old lady", but mature like "young adult" as opposed to "little kid".
I think
Louise is still a filler middle name, and that might contribute to people not wanting to use
Louisa as much.
I like both
Luisa and
Louisa, and I see them differently. I say
Luisa with an "s" sound, and it's more of a pretty ethereal dancer type name. I say
Louisa with a "z" sound and I think it sounds more grown-up and competent but just slightly less graceful.
Luisa and
Louisa are both a lot better then
Louise!!
I have a 30-something cousin named
Louisa.