But, there is the possibility that one could be a fan of both. I love Star Trek, despite the fact that it too rarely depicts hard SF. As for Klingon and Vulcan stories - I accept them when they explore the anthropological issues - but I abhor them when they are just a modern day Commies vs Yanks setup. In any case, the shows that really capture my imagination are ones like "Devil in the Dark" and "Wink of an Eye" and "City on the Edge of Forever" - which is, perhaps, the only time that Star Trek truly succeeded with a time travel story. I love Firefly, but I don't even try to equate it with SF. It's a comedy frontiersman show, which is only set in space because the west is no longer the frontier. It has great entertainment value - but more for the characters and comedy than for any relation to science fiction - as there really is none to be found on the show.