I like them both just about evenly.
Fiona has a light, pleasant sound.
Daphne is perhaps more quirky.
Daphne would turn my head more but
Fiona would blend in better.
I would go with
Fiona.
Daphne isn't totally "out there" but I think
Fiona is more user-friendly. Your daughter might thank you for it. :-) Plus, I think it would sound very pretty paired with any of the names on your list as a middle name, should you choose to go that route.
Not that you asked, but I think
Fern and
Phoebe "feel" similar. I have the same sort of regard for them--they're not my favorites, but I can find many things to like about them.