Update: 5 Seconds of Summer won this round. Click here to vote for their 5SOS Fam in the Semi-Finals!

There's nothing quite like being part of a hugely devoted fanbase. That's why we're using this year's March Madness to fulfill the age-old question: Who has the best fans? For round one, we're putting 5 Seconds of Summer's 5SOS Fam up against the Vamps' Vamps Family. Which group has the better fanbase?

5 Seconds of Summer clawed their way out of One Direction's shadow and managed to cultivate a strong fanbase of their own. When Abigail Breslin wrote a diss-track that was supposedly about Michael Clifford, fans were all over it -- like melted ice cream on your hands when it's 110 degrees outside. Our favorite thing about 5SOS fans is their self-chosen moniker -- because a fandom really can be like a little family sometimes: Complete with fighting, making up and the random black sheep no one likes to talk to, but everyone knows is there.

The Vamps' fanbase has something in common with 5 Seconds of Summer's: They, too, refer to themselves as a family. Known as the Vamps Family, fans of the British pop band are just as intense. One time, fans got a little too overzealous and wound up injuring James McVey. Of course, one tiny group does not necessarily represent the whole, and we're aware that most fans are harmless. Devoted, but harmless. Which is the best way to be, really.

Vote for your preferred fanbase in the poll below! You can vote once per hour until the polls close at 3PM ET on March 17. Remember, neither can live while the other survives.