Battle of the Bands: No longer a tradition exclusively reserved for your high school's grungy disciples of hair-raising metal. In 2015, it's all about the pop ensembles, and PopCrush needs your help naming one multi-member act a champion above the others.

After having crowned Harry Styles and Mahogany Lox our official King and Queen of Young Hollywood, respectively, we're looking to outfit the stars' kingdom with additional pop royals, and in one of our tournament's first rounds, we're pitting two international acts against each other—but only one can survive this World War.

In one corner: Rixton, the British pop rock foursome who similarly garnered attention through YouTube performances before Scooter Braun signed them to his SB Projects in 2012. Their debut studio album, Let the Road, hit stores in March and included singles "Me and My Broken Heart," which sampled a chorus from Rob Thomas' catalog, and "Hotel Ceiling," which Ed Sheeran co-wrote.

In the other corner: 5 Seconds of Summer, the Aussie pop punk quartet that got their start via YouTube in 2011. The group's first album, an eponymous effort that spawned the singles "Amnesia" and "Good Girls," debuted at No. 1 on the Billboard 200, making 5SOS the first Australian act to reach the top spot with a debut. Most recently, they performed "She's Kinda Hot" at the Teen Choice Awards and are gearing up for the release of their sophomore album, Sounds Good Feels Good, which will hit stores later this month.

So, which troupe will trounce the other? Cast your vote in the first round of PopCrush's Battle of the Bands until October 12 at 5 PM EST. We'll announce which of these contestants will take one step closer to pop group glory shortly thereafter!

UPDATE: This round is now closed. Please vote in the semi-finals...

Think you really know 5SOS? Test your knowledge:

See Rixton's and other artists' advice to their past selves: