The poll is closed, but I'd add another vote for Dark here.
Dark is not only cool but useful, both in type-advantages, but also available moves and Pokémon.
Steel, so far, seems pointless to me. It's similar to Rock, with a focus on defense, and low speed... not very useful for me, overall. The Pokémon and moves of this type aren't that great either, with minor exceptions (the Aron line comes to mind).