In the Sky vs. Virgin Media debate, both companies have something the other can't offer to the same high-standard. For Sky, it's their extensive HD content. For Virgin, it's their Video-On-Demand...
I'm a Virgin Media customer, mainly because my house came equipped with cable and it seemed silly not to use it. Their 3-for-1 deal (internet, TV and phone for £30) also seemed too good to miss, and that's another key reason I haven't defected to Sky in three years.
But, as a fan of HD, Sky do come very close to persuading me to sign up with them. Particularly when their Sky+HD boxes came down from £150 to £75 last autumn. But, really, with Virgin now offering Sky channels on their line-up again, I can't justify spending the approx. £15 more per month for a Sky+HD box. Plus, I always hear horror stories about people unable to cancel their Sky subscription -- with telephonists hanging up on customers if they get the impression they've called to leave!
I'm also of the opinion that Virgin's VOD is a secret weapon Sky should be getting very, very worried about. Unlike the satellite-based Sky, Virgin's fibre optic cables can stream content to individual customers. The BBC's excellent iPlayer is part of the VOD suite, and a selection of shows from Channel 4, More4 and E4 are also available (as part of 4OD). Today, Virgin have announced that ITV are joining the fun, meaning that Virgin customers now have access to pretty much every major television network's best shows, 24/7.
Sky will argue that their Sky+ boxes give customers the same experience as Virgin VOD. But there's a key difference: with Sky, you have to manually tell your box to record certain shows and "series link" your favourite shows. Don't get me wrong, Sky+ is a wonderful idea (so good that Virgin copied it with their inferior Virgin+ boxes), but it relies on customers having the time and inclination to scroll through their EPG and tirelessly select what they want recording.
With Virgin's VOD, nearly everything is automatically saved at Virgin HQ and made available, well, on demand. The content isn't stored as data on your set-top box's hard-drive, and we all know how quickly Sky+ boxes can reach full capacity. Virgin's content is all stored on huge servers somewhere, piped to your television at the push of a button.
There are downsides to Virgin, of course. I can't talk from personal experience, but Virgin+ boxes apparently don't hold a candle to their Sky+ counterparty. More annoying is the paucity of HD content with Virgin. If you buy Virgin+ to enjoy HD, be aware that you'll only currently be able to receive BBC HD and a few on-demand movies. Compared to Sky's litany of HD channels, that's a terrible shame. I can understand Sky not letting Virgin carry their homegrown HD channels, but it's a pity Virgin don't yet carry ITV HD or Channel 4 HD. Freesat is currently the best non-Sky option for HD lovers, although Virgin have claimed there will be a significant HD content increase this year.
Ultimately, what's good for one person might not suit another. If you're desperate to get HD (and can afford the £75-£150 box, additional £10 HD fee each month, plus your existing subscription rate), then go for Sky. If you value a vast library of catch-up TV available 24/7 with very little hassle, then go for Virgin. I personally like how you only rent your Virgin box, too, unlike Sky. Virgin+ comes at a price, but nothing like what Sky demand.