The X Factor: Simon and Demi Get Snippy

America is finally getting the chance to vote — again! The X Factor is turning the competition over to viewer votes to determine who will stay and who will go, beginning Wednesday with live performances by the Top 12 on the theme "Songs from the Movies."

But wait, not so fast. The Top 12 turned into 13, as hosts Khloe Kardashian and Mario Lopez revealed a twist at the start of the show — that one of the contestants who was cut from the Top 16 last week would be returning. "The final 12 we're very happy with, but we believe we made a mistake," Simon Cowell explained. Which singer was stellar enough to return? Diamond White of course! The 13-year-old had sung for her life last week, but was let go, much to the disappointment of rather vocal fans.

Now that the contestants must connect with at-home viewers to advance in the competition, the show also started to get heavily into each of their backstories — revealing, for instance, that Vino Alan often performs for the troops, that Jennel Garcia would probably be enrolled in bartending school if she wasn't doing the show, and that Beatrice Miller has two moms.

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Things got a little testy between Cowell and Demi Lovato early on, when Cowell cautioned Lovato and Britney Spears (the two new judges on the panel) against turning the show into a "karaoke competition." From that point, it seemed that Cowell and Lovato were just trying to one-up the other, each sniping about the other's mentoring style and not having a positive thing to say about any of their protégés (at least until Lyric 145 took the stage).

Read on to find out how each contestant did, and which performance(s) the judges thought were "perfect."

The Teens, mentored by Britney Spears

Arin Ray: Ray opened the show with Kanye West's "American Boy," giving a lively performance that prompted Simon to tell him that he was "turning into a little pop star." Lovato and L.A. Reid also heaped on the praise, and Ray showed that he knows how to work the crowd as well — bending down during the song to shake hands with the (mostly female) audience members in the front row, and telling Kardashian and Lopez afterwards that he was there for the fans.

Beatrice Miller: Miller chose the Goo Goo Dolls' "Iris" for her song, and while the recorded version sounded like her 13-year-old voice wasn't mature enough for the vocals, apparently something was lost in translation from the live versionbecause all the judges had great things to say. Reid even told Miller her vocal tone "sounds like a hit record." And her mentor, Spears, said her musical talents weren't the only thing that would win her admirers. "You have the best personality out of anybody in this whole competition," Spears told her.

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Diamond White: Suffice to say, all the judges welcomed White back into the competition with open arms. For her comeback song, the teen offered a rendition of Whitney Houston's "I Have Nothing" that far surpassed her 13 years. Reid called the song choice "ambitious" but said White rose to the occasion, and Lovato said the performance nearly moved her to tears.

Carly Rose Sonenclar: Sonenclar redeemed herself from last week's choreographed dance extravaganza with Bruno Mars' "It Will Rain," which was much more her speed. "This week compared to last week, it's night and day. This is you in your element," Lovato told her. Cowell agreed that it was "a huge improvement" and said he felt like they were "watching a star in the making." As for her mentor? Spears told Sonenclar she should have been the final performer of the night "because nobody can follow that."

The Young Adults, mentored by Demi Lovato

Paige Thomas: Thomas gave a straightforward rendition of Berlin's "Take My Breath Away" that left the judges impressed but not "blown away," in the words of Reid. It was Thomas's performance that prompted Cowell's comment about the "karaoke competition." And his criticisms continued with ...

Jennel Garcia: Garcia went full rocker chick this week, tackling Joan Jett's "I Love Rock 'n' Roll." Unfortunately, neither Reid nor Cowell were on board with her new look. Reid called it a "Joan Jett parody," and Cowell also criticized Lovato' altering her performance, telling Jennel she was "unrecognizable from the person" who originally auditioned for the show. "That's why I'm her mentor and you're not," Lovato sniped back.

CeCe Frey: After ditching her signature leopard face paint last week, Frey was back in big cat mode Wednesday as she powered her way through Survivor's "Eye of the Tiger." Spears called her performance "courageous," but Reid and Cowell were more tepid. Cowell in particular didn't mince words. "Anything recognizable about you from the beginning has been thrown away, and this song choice was just horrible," he said, criticizing Lovato's unoriginality and lack of imagination and telling Frey she should start picking her own songs. "You are being taken into a direction you shouldn't be going into." (Frey, for the record, said she was on board with the song choice.)

The Over 25s, mentored by L.A. Reid

Vino Alan: Alan took on Percy Sledge's "When a Man Loves a Woman," and Reid said the rendition made him proud. Lovato was more reserved, however, telling Alan that her main concern "is that I have a hard time seeing you as a No. 1artist. I think you're an incredible vocalist, but I'm not sure I see you as a pop star." Cowell, on the other hand, said the performance took Alan "from zero to hero" in the span of a week and called Lovato's comment about him not being a rock star "stupid."

Tate Stevens: Stevens's country-tinged take on Bon Jovi's "Wanted Dead or Alive" led Spears to tell him, "You definitely are a true cowboy, and you're a slice of America. You nailed it." And even Lovato and Cowell both agreed that he's one of their favorite contestants.

Jason Brock: The judges (save for his mentor Reid) were unimpressed with Brock's delivery of R. Kelly's "I Believe I Can Fly." Clad in a bright red tuxedo jacket and using a sparkly microphone, Brock offered a straightforward rendition of the ballad that Spears said reminded her of a "Vegas lounge act" and Lovato called "predictable and very cabaret." Cowell, never one to shy away from being a little mean, told the portly Brock point-blank, "I don't believe you could fly. Maybe jump a couple of inches off the ground." Possibly trying to heal his protégés presumably battered ego, Reid reminded Brock that the decision of whether he will stay or go is up to the audience at home, not the judges.

The Groups, mentored by Simon Cowell

Emblem 3: The all-male trio is quickly becoming a frontrunner in the competition, delivering a pop mashup that included The Temptations, Katy Perry and One Direction. Reid struggled to find something constructive to say afterwards, and finally gave up. "You guys are actually perfect and I don't like that," he told them. Lovato, trying to get in her own dig at Simon, criticized his decision to include another one of his groups (One Direction) in the mashup. "They deserve better than that," she said. "That's called being clever," Cowell responded testily.

Lyric 145: Lyric 145 went for musicality and theatrics, blending Mary Poppins and Alice in Wonderland as they dressed up as the Mad Hatter, the Cheshire Cat and the Red Queen for a hip-hop version of "Supercalifragilisticexpialidocious" that Reid called "inventive" — even though he wasn't a fan. "I completely hated it, but you shouldn't be bothered," Reid said. "It's not my personal cup of tea, but I think it was perfect." Spears also gave a thumbs up, and even Lovato had only good things to say. "Who knew in that rusty old brain there was some fresh, cool, hip thoughts?" she said, referring to Cowell, who told the group they were "bloody fantastic."

Fifth Harmony: Formerly known as 1432, and before that as Lylas, the newly-named Fifth Harmony (let's hope this one sticks!) proved that they're the group with the most harmony between them — at least vocally speaking — as they chose to cover Christina Perri's "A Thousand Years." Reid said they "nailed it," and Cowell called their vocals "stunning." "The transformation week on week has been enormous," he told the all-female quintet. "I could not be more proud of you girls."

So what did you think? Were the judges right to bring Diamond White back into the competition? And which contestant will be getting your vote? Sound off below!

The X Factor results show will air Thursday at 8/7c on Fox, and will also feature a performance by One Direction.