Neither, really. Women named
Abby,
Abbie and
Ally,
Allie are everywhere (I prefer the
Abbie and
Allie spellings).
Alison is nicer than
Allison, but still feels a bit 70s.
Abigail feels 80s/90s.
I guess I would pick
Abigail, as the full name is fun to say. Not a fan of
Abbie etc.