The quality of PVC gear varies widely. Polyurethane is a rubber polymer coating. It's lighter and more flexible than PVC, but it's also less durable, and is usually applied inside the nylon shell. It's more breathable than PVC, but making it more breathable on the inside means reducing its ability to repel water from the outside. Better quality polyurethane gear is carefully bonded in many thin layers to prevent water absorption that can result in eventual delamination.
Neoprene is the most flexible and durable of the coatings.
It's very popular in England and other areas where boating is not just wet, but cold, and boaters are willing to suffer the weight and the cost for guaranteed waterproof gear that lasts. Breathable fabrics allow perspiration and condensation inside the suit to pass outward. Body heat and the higher pressure of humidity drive out the weather vapor. Some breathable gear is designed to wick water away from the skin. What to Look For If you are considering non-breathable foul weather gear, look for an inner lining coated with urethane or some other material that allows condensation to collect on the outer shell without drenching you inside, and look for an open bottom or netting that allows the water to drain.