The singing contest's two-hour show, which culminated in Christopher Maloney's exit, averaged 9.29m (a 38.4% share) between 8pm and 10pm, adding 209,000 on ITV1 +1 while 960k (5.1%) caught The Xtra Factor on ITV2.
Although The X Factor made a week-on-week improvement of almost 2m, the figure represents a 12% drop on the last Saturday show of last year, and an even steeper 34% decline on the 14.1m audience for Cher Lloyd's departure in 2010.
Strictly Come Dancing topped the Saturday ratings with a huge 10.75m (45.3%) between 6.45pm and 8pm for week ten of the resurgent BBC One ballroom dancing show, up a million on last week.
Last night's Strictly achieved a series high peak of 12.2m, while X Factor managed a 5-minute high of just over 10m.
As consistent as usual, Merlin pulled in 5.54m (22.4%) in the 8pm slot, but BBC One lost momentum later in the evening with The National Lottery Awards Show (2.7m/11.4%) and Casualty (3.81m/16.2%). Match of the Day scored 3.46m (22.4%) from 10.30pm.
Elsewhere, Channel 4's screening of the film Predators pulled in 1.24m (5.8%), nearly three hours of snooker averaged 1.02m (4.2%) over on BBC Two, and Single Santa Meets Mrs Santa Clause got 1.37m (6.8%) into the festive spirit on Channel 5 from 5.30pm (+1: 126k).
Overall, ITV1 pipped BBC One in primetime with 25.4% (+1: 0.8%) against 24.9%. BBC Two was far behind in third with 4.3%, edging Channel 5's 4.2% (+1: 0.4%) by the narrowest of margins. Channel 4 followed in last place with 3.9% (+1: 0.7%).
BARB ratings data supplied by Attentional