My daughter's done both and enjoyed both.
The mermaid package is awesome, but your DD will need to able to sit still for a long time. It takes quite a while to apply all that make up. That said, my DD loved it, once it was done. She still wears the accessories she got with the package.
I'd book PL, then keep trying for BBB, if you want.
I think if I asked my DD, she'd rather do PL again, though.