I would avoid the Teflon version. Teflon cold-flows too easily and a denser plastic works just as well. Cheaper too. Plain old Delrin, Nylon, or Polyethylene is a better choice.
You'll never wear one out from towing, but you may break them during hitch-up. Especially if you get one too big for your pin box. Other than that, just the retaining fingers as others mentioned.