Ranger is spot on as usual with the state of our copper in the UK. I got DSL a while ago and it dropperd regularly plus gave me noise on the line you could hear through the phone despite trying several filters. Despite several fault calls it was always "no fault found" until one day (to my delight) the whole line went dead, phone and all. Finally they had to do something about it, and the result was a repaired and much quieter phone line and a greatly improved DSL service that runs faster and hasn't dropped in months! Also I've spoken to an employee of our major Telco here who says that engineers might be given thirty or more DSLs to enable per day and some of them just go along the punch-down blocks half-heartedly while dreaming of lunch. He'd personally remade the copper-side conections for a few subscribers and vastly improved the service each time.
Having said all that, though, I'm sure cable has it's own set of technical problems but perhaps the biggest issue here is that you can get DSL from big, established national telco whereas cable is provided by smaller, newer, more exposed companies with fewer resources and you sometimes get a poorer customer experience. As they say in Yorkshire where I come from, "You pays your money and you takes your choice..."