Ehh, its pretty close between the Dark BrotherHood and the Companions. The Dark Brotherhood definitely wins the awards for badassness and visual appeal, but the Companions just seems more.....likeable. The Companions are much more like a family which I think is important when it comes to factions, and they also much more respectable in the world of Skyrim. However, if I were to pick one, i think I would still pick the Dark Brotherhood.