PCV is
poly-
vinyl-
chlorine, and is a huge environmental nightmare. The dioxin pollution from PVC manufacture is horrific, and if burned and/or landfilled when you're done using them, dioxin, lead, and other contaminants are released. There are other nasties, but, this seems enough to list here. You can do a search; I used "pvc environmental pollution", and got several nice links. The one below is the one of the more terse summaries:
http://www.healthybuilding.net/pvc/T...VCSummary.html
I avoid PVC like the plague, at home and on my bike.
I have the plus fabric, traditional (hood-over-top) style. I like them very much. The fabric is lightweight but strong. I use them for commuting as well as touring. I've put books, glass-jar quarts of milk, and clothes, and they hold up just fine. I'm not sure anything will stop a pitbull from biting through anything, but I'm also not buying everything to withstand a pitbull. If so, I'd end up riding a car.