Here are all the official ratings for Strictly and X Factor when they have been shown on the same day, between 2004 and 2008. I have bolded the higher rating in each case.
In 2004, every single episode of Strictly beat the equivalent X Factor.
30 October 2004
Strictly (7.46m), X Factor (6.53m)
Strictly Results (8.23m), X Factor Results (7.26m)
6 November 2004
Strictly (7.33m), X Factor (6.89m)
Strictly Results (8.72m), X Factor Results (7.02m)
13 November 2004
Strictly (8.81m), X Factor (7.42m)
Strictly Results (MISSING from BARB site!), X Factor Results (6.88m)
20 November 2004
Strictly (8.71m), X Factor (7.91m)
Strictly Results (9.39m), X Factor Results (7.98m)
27 November 2004
Strictly (8.10m), X Factor (8.06m)
Strictly Results (8.82m), X Factor Results (8.01m)
4 December 2004
Strictly (8.53m), X Factor (7.79m)
Strictly Results (8.62m), X Factor Results (7.52m)
11 December 2004
Strictly Final (9.70m), X Factor Final (8.62m)
Strictly Final Results (11.60m), X Factor Final Results (9.96m)
In 2005, The X Factor had a lead in the earlier weeks until Strictly took over for a few weeks in November, and again for the Semi Final and Final. X Factor was usually ahead for the Results show. Overall, The X Factor had a slightly higher series average than Strictly.
22 October 2005
Strictly 7.15m, X Factor (8.47m)
Strictly 7.07m, X Factor Results (9.02m)
29 October 2005
Strictly 7.83m, X Factor (8.60m)
Strictly 7.03m, X Factor Results (9.52m)
5 November 2005
Strictly 7.23m, X Factor (7.76m)
Strictly 6.98m, X Factor Results (7.51m)
12 November 2005
Strictly (9.45m), X Factor (9.09m)
Strictly Results (8.02m – now missing from BARB site for some reason), X Factor Results (8.99m)
19 November 2005
Strictly (9.10m), X Factor (8.95m)
Strictly Results (7.87m), X Factor Results (8.76m)
26 November 2005
Strictly (9.44m), X Factor (8.45m)
Strictly Results (7.53m), X Factor Results (9.13m)
3 December 2005
Strictly (9.08m), X Factor (10.00m)
Strictly Results (7.68m), X Factor Results (8.95m)
10 December 2005
Strictly (9.61m), X Factor (7.80m)
Strictly Results (9.14m), X Factor Results (8.48m)
17 December 2005
Strictly Final (10.76m), X Factor Final (9.65m)
Strictly Final Results (10.55m), X Factor Final Results (9.90m)
In 2006, The X Factor tended to be in front for the first few weeks, with Strictly taking a lead in November, before X Factor retook the lead. Overall, honours even – with 11 wins each, but Strictly had a much higher series average.
7 October 2006
Strictly (9.23m), X Factor (6.77m)
Strictly Results (7.62m), X Factor Results (8.95m)
14 October 2006
Strictly (6.71m), X Factor (7.52m)
Strictly Results (6.78m), X Factor Results (7.38m)
21 October 2006
Strictly (7.18m), X Factor (7.54m)
Strictly Results (7.85m), X Factor Results (7.70m)
28 October 2006
Strictly (7.73m), X Factor (7.10m)
Strictly Results (7.91m), X Factor Results (7.52m)
4 November 2006
Strictly (8.48m), X Factor (7.30m)
Strictly Results (7.94m), X Factor Results (7.91m)
11 November 2006
Strictly (9.30m), X Factor (9.83m)
Strictly Results (8.68m – now missing from BARB site for some reason!), X Factor Results (8.24m)
18 November 2006
Strictly (9.66m), X Factor (9.22m)
Strictly Results (7.73m), X Factor Results (8.80m)
25 November 2006
Strictly (9.20m), X Factor (8.46m)
Strictly Results (7.44m), X Factor Results (8.69m)
3 December 2006
Strictly (8.85m), X Factor (9.31m)
Strictly Results (7.92m), X Factor Results (8.24m)
10 December 2006
Strictly 9.24m, X Factor (8.39m)
Strictly 10.33m, X Factor Results (8.25m)
17 December 2006
Strictly (Semi Final) 9.45m, X Factor Final (10.52m)
Strictly (Semi Final Results) 7.42m, X Factor Final Results (10.78m)
In 2007, Strictly moved its Results show to a Sunday. However, on the Saturday shows, after the first three weeks of X Factor victories, Strictly beat the two X Factor shows every week. Only when we got to the X Factor Final, on the same night as the Strictly Semi Final, did X Factor manage to pull ahead again. Overall, Strictly once again had a higher series average than The X Factor.
29 September 2007
Strictly (4.87m), X Factor (6.42)
6 October 2007
Strictly (7.68m), X Factor (8.08m)
7 October 2007
Strictly (7.03m), X Factor (7.92m)
13-14 October 2007
Strictly (8.51m and 8.15m), No X Factor shown!
20 October 2007
Strictly (7.69m), X Factor (6.60m and 7.07m)
27 October 2007
Strictly (8.28m), X Factor (7.51m and 7.51m)
3 November 2007
Strictly (9.25m), X Factor (8.47m and 6.99m)
10 November 2007
Strictly (9.65m), X Factor (9.18m and 8.59m)
17 November 2007
Strictly (9.41m), X Factor (9.15m and 8.05m)
24 November 2007
Strictly (9.70m), X Factor (9.30m and 8.88m)
1 December 2007
Strictly (10.22m), X Factor (9.56m and 7.82m)
8 December 2007
Strictly (10.45m), X Factor (9.83m and 9.62m)
15 December 2007
Strictly Semi Final (10.97m), X Factor Final (11.78m and 12.23m)
In 2008, roles were reversed, with X Factor beating Strictly nearly every week. Strictly still had Results on Sundays (except on 15 November and 13/20 December), X Factor was mainly still a Saturday-only show, except for bootcamp.
As you can see below, 27 September 2008 is the last time Strictly beat X Factor on final figures.
13 September 2008
Strictly (6.22m), X Factor (9.96m)
20 September 2008
Strictly (8.48m), X Factor (10.01m)
27 September 2008
Strictly (9.02m), X Factor (8.94m)
28 September 2008
Strictly (8.44m), X Factor (9.07m)
4 October 2008
Strictly (9.66m), X Factor (10.84m)
5 October 2008
Strictly (8.60m), X Factor (10.11m)
11 October 2008
Strictly (7.79m), X Factor (11.09m and 9.05m)
18 October 2008
Strictly (8.99m), X Factor (10.21m and 9.13m)
25 October 2008
Strictly (9.75m), X Factor (10.37m and 8.89m)
1 November 2008
Strictly (9.79m), X Factor (11.65m and 9.72m)
8 November 2008
Strictly (10.04m), X Factor (10.72m and 9.46m)
15 November 2008
Strictly (10.03m), X Factor (11.28m)
Strictly Results (9.76m), X Factor Results (10.62m)
22 November 2008
Strictly (10.75m), X Factor (11.77m and 9.98m)
29 November 2008
Strictly (10.51m), X Factor (12.67m and 11.41m)
6 December 2008
Strictly (9.75m), X Factor (10.30m and 10.60m)
13 December 2008
Strictly Semi Final (10.37m), X Factor (13.77m)
Strictly Semi Final Results (9.58m), X Factor Results (14.06m)
I won't post all the figures since then, but the gap widened between the two in 2009, with The X Factor getting a much higher rating every week. Both series had their best ever year in 2010, but The X Factor was still well ahead of Strictly for every single week.