The winner of the NBC reality show, who will pocket a $1 million prize and the chance to headline a Las Vegas show, will be announced on Wednesday night.
Here's what the judges had to say:
Piers: "I've waited the whole time for this to click into place and then tonight, out she comes the little diva and sings better than ever. And then you two come, the brothers, and it all works! You brought your mum out of a coma and tonight you may well give her a cheque for a million dollars, it was that good."
Sharon: "Everything was just perfectly in sync. It all came together. We knew you had it in you and you delivered it for us tonight. You should be so proud of yourself. It was fantastic."
David: "You not only brought your mum out a coma, you also brought Piers out of a coma! You guys hit it out of the park! Slam dunk! The best ever! Congratulations, you sounded fantastic!"
Sharon: "You took a real risk and gave a very emotional performance and I think you did the right thing. At first everybody was really worried because it's just you and the stage. But I loved your music choice and you did well, you should be proud of yourself."
David: "I loved the way it started out and then you went on to this [solo routine]. If you continued on to do a Las Vegas show, bring that back and complete the same act. Tie it all together and I think it would be great."
Piers: "I love you as a person but I will be very honest. I don't think that routine worked. If you did it after your audition and that's all we knew about you [maybe it would]. But once we saw you in a group with other dancers, it took it onto a different level. Tonight you went back and it was wrong because it lost the fun that made you what I love. It's not irredeemable, you're still a good act but tonight that did not work."
David: "It has been a real honour and pleasure to be a part of your journey. You came on here so humble and now you are leaving us a star. Whether you win or not, you will be working, playing stages all over the world. That was a fantastic, slick, cool performance and well worthy of Vegas."
Piers: "You are the new Barry White! But, it's not quite there yet because Barry was the love god and I wasn't quite feeling love tonight. When you got to the women, I thought Barry would have scooped them up and that would have been the last we saw of them! You got there like a frightened rabbit in headlights. We need a bit more love! But fantastic vocals."
Sharon: "I thought it was very comfortable, probably the most comfortable I've seen you up there. It was a very natural, relaxed performance and it was perfect for your vocal range."
Piers: "One of my favourite movie scenes is in An Officer And A Gentleman when Richard Gere in the white suit swoops up Debra Winger and swings her out of the factory into her dream. I think there are millions of Americans watching you and thinking, 'She is one of us and she is living our dream'. And they are all going, 'Way to go!'"
Sharon: "It seems like yesterday when you came in and auditioned for us in your short summer dress and here you are looking a billion dollars and sounding like three billion. It's incredible - you've come such a long way in a short time so imagine what you will be like in a year's time! It's just going to get better and better."
David: "It's like looking at Audrey Hepburn. You are so beautiful and you command the stage, attention and our respect. Forget Vegas, you are going to play bigger halls. The world is your stage and it is all waiting for you."
Sharon: "That was beautifully choreographed and it was fantastic. The whole stage was so Vegasy, I felt I was there. You girls belong in Vegas, however this competition tonight is so tough. You are all so good and it's going to be so hard for the voter."
David: "Do you girls ever stop smiling?! How do you sleep at night? I can't stop smiling watching you. You are terrific and bring such happiness and energy to the stage every time."
Piers: "What is extraordinary is that you are sisters and have presumably danced all your lives together but you still look like the best of friends! What it's given you is a tremendous chemistry and it's like you are one when you dance and it's amazingly infectious. I also think we're seeing an act that has put more hours into what they do than any other act."
David: "You guys have a lot of guts doing a Frank Sinatra song. I was going, 'Oh my God, this is going to be horrible'. But it was terrific and you did it your way! You came out here and took a shot. You have gone cheesy, like you've done before, but came out and did it your way."
Piers: "What do you mean they could have gone cheesy? That was the cheesiest thing I have ever seen in the history of cheese! I could feel the mozzarella seeping off the stage! But, here's the thing. I was walking on Malibu beach this week and started singing 'Unchained Melody' and realised it was your version! You have become my guilty pleasure! That is cheesy, Vegas is cheesy in many parts and I think it is fabulous cheese!"
Sharon: "It was triple cheese tonight but your vocals are perfect, the harmonies are superb and you gave such great performances. You were very strong up there, you command the audience. As I've said before, I love cheese and I love you guys."
Piers: "I think you gave the best performance you have ever given. I think every time you perform now we feel a bit more embarassed that we left you out of the top 40 because this could be the night when the wildcard goes the whole way."
Sharon: "As a manager, if I was looking for a young guy to be a soft rock singer I would pick you because you just fill all the ticks in all the boxes. You're good-looking, you have a great voice and great likeability. I think your trousers could be tighter, but otherwise you're very, very good and you are a dark horse!"
David: "Is the trouser line a compliment or a criticism? Great job, it was your best performance of the whole season. It was absolutely out of the park and you have a great shot at winning this whole thing."
Sharon: "Before you came on, I said I hope there's no more Piers jokes but this isn't a joke. I think this is a marriage! Your material tonight - the Ryan Seacrest - it just got me. I couldn't stop laughing until the end of your set. Hysterical. It's going to be so hard to choose who's going to win this show.
David: "Every time you come on here, you're funnier and funnier and you absolutely deserve to be where you are at. It will be very hard to vote against you. Fantastic... and can I be at the delivery of your baby?"
Piers: "You shameless little hussy! First you cheat on me with The Hoff and now Simon Cowell! Hasn't he got enough women? I want a paternity test and I want it urgently because if you win the $1 million I want my slice of the pie!"
David: "You have been one of my favourites from the beginning because you are what this show is about. It's so fantastic seeing you sitting there and being a part of your journey. You probably sat at home on your porch and thought, 'I like that show and maybe I'll be in the final'. Maybe some day, you will win this."
Piers: "It wasn't perfect, you missed the odd note and it was a little flat in places but this is almost the point of you. You are a rough diamond. You are unpolished and probably need professional training, but at your heart you are what this show was created for."
Sharon: "So what if you don't have the best voice in the contest, you don't need to. Some of the greatest icons in ths industry like Johnny Cash, Bob Dylan, Mick Jagger and Lou Reed didn't have the best voice. But they are all such indiviudals and unique and you are very, very unique."
Piers: "That was an absolutely brilliant way to end a brilliant show. You are the most creative act we've seen and the most dynamic. I think the most exciting. I would put you in Vegas tomorrow."
Sharon: "I have to hand it too you, you are all so creative. I don't how you come up with these different things each time you perform for us, but I'm glad you do. You really do belong in Vegas."
David: "You guys are insane! You make me want to beat on things and now you make me want to take a shower and put drums in the shower and drum and shower all day! Each time you come on, you do wackier things and that's what the entertainment value is. You belong in Vegas, what a great way to end the show on such a high note."
All pictures Copyright: NBC