The Banshee has an ability that each time it deals combat damage, the defending player discards a card. In a 3 or 4 player game, the Banshee can generate decent card advantage, especially if you happen to play a deck that benefits from opponent’s discarding cards. Commanders such as Nath of the Gilt-Leaf or Crosis the Purger will happily take Banshee of the Dread Choir into their ranks.
Another Commander that would like the Banshee is Vela the Night Clad. Since Vela gives the Banshee Intimidate, players not controlling an artifact or Black creature won’t be able to block the Banshee, meaning instant discard. Also, because the tokens that Banshee creates must be exiled at end of turn, it makes sense to find a way to sacrifice them. If you can, Vela makes each of your opponents lose 1 life for each token. Any Black deck that benefits from sacrifices like this may find a home for the Banshee, as long as you have the sacrifice outlet before their necessary exile, which won't benefit you at all. While the Banshee is a bit of a niche card, she’s a decent one.