Black Kuhli Loaches or Cory Catfish?

Corydoras are cool fish, come in many varieties, and are pretty hardy. I would not have a community tank without at least one, and if space is available, they are entertaining in schools. Kuhli loaches, although entertaining as well, will hide, less so in numbers, but are a little more fragile than Corys. With your space I'd go with a cool Cory.