UPDATE: Justin Bieber won! Vote for him in the next Pop Clash battle here.

Last week, Britney Spears ousted returning champ Cher Lloyd to become the reigning winner of Pop Clash! Now Brit's 'Work Bitch' will face off against Justin Bieber's 'Heartbreaker.'

Britney's new single proved that she's still got it. Sounding as fierce as she did back in her '...Baby, One More Time' days, Brit advocates working for what you want. The mother of two definitely can both walk the walk and talk the talk! In recent years she's toned up and scored a Las Vegas residency. If anyone knows how to "work," it's Britney!

Justin Bieber has also been working it. The singer has been touring the world, but still managed to drop 'Heartbreaker.' The track emphasizes JB's R&B influences, allowing Bieber to croon to his heart's content. The song shows his personal growth, as he owns up to his own imperfections.

Who should win this week’s Pop Clash: Britney Spears or Justin Bieber? You can vote once per hour until the poll closes at 3PM ET on Oct. 21.

Watch the Britney Spears 'Work Bitch' Video

Listen to Justin Bieber, 'Heartbreaker'