What's the most pointless rivalry or schism in all of fandom?

The great thing about science fiction and fantasy is that there's a nearly limitless amount of books, movies, TV shows and comics to celebrate. But sometimes, people decide that you can only be a fan of one thing or another. You have to choose. What's the most pointless rivalry in all of fandom?

Please include a picture that shows off the dueling entities or universes. And please be nice and considerate to each other!