What makes this plastic so dangerous is the very toxic chemical it releases and creates called dioxin.

When products containing PVCs are discarded they create additional dangers to our environment because PVCs are not recyclable and therefore end up in our landfills. Other PVC based products that are not discarded in landfills are incinerated and this causes additional danger because PVC’s release toxic dioxin when incinerated.

PVC is also difficult to recycle so therefore much of it ends up in our landfills; but perhaps the greatest danger of PVC is the phthalates that are added to it to make it softer and more pliable. Children’s toys use the soft version of this PVC! The phthalates are well known endocrine disruptors that can cause harm to the reproductive system of both males and females.

The knowledge that PVC is dangerous is rapidly spreading. It has hit the corporate mainstream, that companies such as Wal-Mart, Nike, IKEA, and The Body Shop have begun to phase it out of their products. Consumers are waking up to the dangers of PVC and are putting the pressure on other companies to begin the phase-out process as well.

PET is definitely a more sustainable choice of material than PVC. The "Chloride" in PVC is what is not considered "environmentally friendly". PVC does release carcinogens when incinerated and can to some degree when processed. Burning PVC creates the incredibly dangerous by-product dioxin. This characteristic makes it by far the most "troubled" of the two materials.

“No single material shows up as the best across all the human health and environmental impact categories, nor as the worst but the risk of dioxin emissions puts PVC consistently among the worst materials for human health impacts.”

Our candles Vestina are made of ecologically acceptable materials (PET, PP). Compare to other electronic candles it can be easily and completely dismantled, as batteries are not enclosed in wax. Vestina candles are environmentally friendly: after use it can be dismantled and ecologically disposed off. 

Source:
http://www.greenerpackage.com/discuss/sourcing_renewable/pvc_vs_pet
http://www.bellaonline.com/articles/art47053.asp
http://www.naturemoms.com/blog/2008/06/02/the-danger-of-phthalates-and-pvc/