A trainer I worked with used the plastic prong with a couple dogs. It seemed to work really well, but then again, I haven't had the metal prongs fail me either! If you decide to go for a prong (plastic or metal) make sure you have someone show you how to fit them properly. A client of mine used the metal prong with their lab, and he didn't give a hoot after the first session. I showed them how to fit it correctly and it made a world of difference.