Britney Spears Faces Off With Christina Aguilera

It's an all-out ratings war as The X Factor's Britney Spears goes up against The Voice's Christina Aguilera. Who will win? INSIDE EDITION has the scoop.

It's Britney Spears vs. Christina Aguilera.

Spears is ready for her debut Wednesday night as a judge on The X Factor. INSIDE EDITION caught up with Simon Cowell, Britney Spears and the other X Factor judges at Grauman's Chinese Theater in Hollywood.

"I'm most excited about my team, of course, winning," said Spears.

But her competition tonight is Christina Aguilera and her show The Voice.

NBC added a third night of The Voice this week and X Factor boss Simon Cowell says the head-to-head battle breaks a gentleman's agreement not to run the two talent shows opposite each other.

Cowell told INSIDE EDITION, "They decided to turn this into a bit of a war by putting their show up against ours. I really hope it backfires because the first episode, and I'm not just saying it, is sensational."

Spears told us, "I'll be nervous before the live shows because I've never done anything like that before." 

Spears and Demi Lovato put their handprints in the cement in front of the legendary theater. Spears, with fiancé Jason Trawick, was all smiles. But taking on her old friend Christina Aguilera wasn't far from her mind.

After all, the two started their careers together. Way back in 1993, 11-year-old Spears shared the stage with 12-year-old Aguilera on the new Mickey Mouse Club.

Now, Spears and Aguilera are butting heads on two of the hottest shows on TV!