I can have either in my house, I currently have Sky HD, simple because I prefer the EPG and whole ease of use, and like the mass of HD channels.
I will jump ship if things change, but the V+HD box (My neighbours all have it) doesn't do it for me, clunky interface, and the quality of stuff using iPlayer/4OD isn't too hot on a large screen..
A few people I know have SKY HD and 50Mb Virgin broadband, best of both worlds, but you pay through the nose for it all..