"The tightly woven cotton is called Ventile, and is used in the damp UK and in the Antarctic. Heavy though.
Uncoated nylon? Ugh!"
Being from the damp UK I can say that Ventile isn't used much for backpacking here. Day hiking yes, because a double Ventile jacket (weighing 2+lbs) will keep you dry in several hours of rain. However it needs drying somewhere warm if it's to keep you dry the next day. I've had a few unpleasant experiences with wet Ventile jackets! If wet Ventile freezes it becomes very stiff – very windproof but uncomfortable. A wet or frozen Ventile jacket is very heavy too, as it absorbs so much moisture.
Uncoated nylon doesn't absorb much moisture of course and dries much, much faster than Ventile. How comfortable it is depends on the type of nylon. Pertex is uncoated nylon.
For cold conditions, damp or dry, I prefer Paramo waterproof clothing, which is as breathable as Ventile but waterproof and fast drying. It's also very comfortable. I have fallen asleep in my sleeping bag wearing a Paramo jacket and trousers – waking in the middle of the night because I was too hot.
As to vapour barriers I've found both vapour liners and clothing effective but never very comfortable. As I haven't had problems keeping down sleeping bags dry even in cold weather for trips of 2-3 weeks, the longest I take in winter, I stopped using VBs.
