I've had both and I'm not sure about Sky being the best....
One thing I find really annoying about sky is when it rains you are likely to lose viewing...Really annoying thing is it's times that the weather is bad that you want to watch the damn thing!!
They could do something about it though because when I've watched a pay per view event or even a match say between Man Utd and Chelscum you don';t get a flicker even if there are hail stones, they choose when to inject more "life" into the receivers...
NTL never had that problem and Sky have only just got around to doing mutli room viewing. Customer Services there isn't much in it, both are crap