I vote nanaly. because she's too OP. despara is good too, but I'd go for nanaly's burst over despara's.
still, no harm playing both. if you ever screw up one account, there's a backup. also helpful when you're entering events somewhat blind. if one side fails or screws up and gets 2* instead, you can use that one as experience and not screw up on the other account (thus getting 3*)