which to fodder which to keep?

nvr really planned on using winter lissa and just wanted one for fodder but somehow i ended up with 2 both being atk+. one is spd-(optimal but superbane) and other is def-(optimal for arena scoring but prob nvr gunna +10 merge). who to keep and who to fodder? as of now i want to keep spd- as i prob wont user her for arena but her spd aint half bad for a armored unit.