Depends how you look at it.
Sky charge £45 per month for all 6 mixes and Sports and Movies. You add in the cost of a BT line and it comes to £55.50 (this is when you are on BT e-bill, it would be £56.75 if you were not)
Virgin is £55.50 when on e-bill for TV XL, phoneline and Sports and Movies (or £56.50 if not). This is with the 1st June price rise
Yes Virgin are 50p more expensive if you were on Sky Line rental @ £10 per month, but if you wanted Setanta, Virgin is still cheaper by £9.99/£9.49
If you are looking at just Sports it would be Sky and BT @ £48.50 (Sky line rental would make is £48) and Virgin @ £48.50. This still doesn't take account on the extra £9.99/£9.49 you need to pay for Setanta