Never mind the battle of the performances (Tulisa's enormous polka dot 'meringue' as the judges first stepped on to the stage.
Kelly's forest-green embellished high-necked dress was more pared down but no less effective with its stunning plunging neckline and fine details.
Both ladies made a quick change before performing with their own acts and, whileKelly donned the prettiest dress of the night: a shimmering gold minidress.
Which dress do you think rocked Wembley best?
See all the picsfrom The X Factor semi final here: