You get 3 different types I think:
Poly pul which is the bog standard pul like Bumgenius and Fuzzis
Laminated cotton which is what most prints are made from (including the HH prints, although the plain HH are poly pul) It is just cotton fabric backed with a waterproof layer, I think people have problems with this as the cotton layer can draw moisture from inside.
Cotton with a hidden layer of pul - this is how the new Pocket Bot plus and Wee Notions cotton pockets are made, it is just pul and cotton sewn together.
Hillary at PB does say that the way she sews the cotton and pul together makes them very reliable but I don't know whether it is true as we have never had any problems with cotton pockets. It does kinda make sense as you could sew it so that the pul layer makes it completely waterproof and then the cotton layer is just sort of put on top but not touching anything on the inside.
Does that make sense?