Today's battle features two male contestants who took part in nail-biting finals. One ended up winning, the other just missed out. But who was the greatest?
Leon Jackson (Series 4 winner) vs Olly Murs (Series 6 runner-up)
Little Leon Jackson is the forgotten man of The X Factor. After pipping Rhydian Roberts to the series four title, things looked bright for the West Lothian warbler, but he was never able to match the mega sales of his debut, a cover of the Whitney & Mariah classic 'When You Believe'.
On the show, Leon was a hugely popular figure and the fact that he managed to beat the tabloid favourite and much glitzier Rhydian was a credit to his likeability as much as his sweet vocals. Could he surprise us all again and be named the 'Ultimate' X Factor act?
Olly may have been pipped to the post by Joe McElderry, but the Murs-inator's career has gone from strength to strength since he danced off the Fountains Studios stage three years ago. What he lacked in vocals, he made up for with charm and fancy footwork.
Scoring chart hits in the UK, touring the US with One Direction, hosting the Xtra Factor, scoring goals in Soccer Aid and making silly hats acceptable again are just a handful of his achievements. Is he the show's greatest ever act?
Olly's showstopping first audition:
Leon's cover of 'When You Believe' in the 'X Factor' final:
Olly Murs - 42.80%
Leon Jackson - 57.20% - WINNER