Which are better? Safer?
(Metal or Plastic Cover plates)

well you shouldn't use a metal blank cover on a plastic box right?, so that would be out....

For most work I prefer the flexible & virtually indestructible nylon plates made by Hubbell. They do have the drawback of not snugging up to the wall as tight as regular plastic & this can be a problem on 3 gang or larger boxes.

Tom

I don't like how the nylon plates "dimple" when the screws are tightened. I guess you have to leave them loose to make it look right. Just has a cheap plastic look compared to the hard plastic ones...(boy that sounds dumb...)

I use metal plates with handy boxes or in commercial applications where metal plates are used elsewhere. (Stainless for food services, etc.)And, yes, only with metal boxes.

I do have concerns about the covers having enough ampacity to trip the OCPD during a short to ground. Joe's pics in the violations section give me such a concern.

In using deep handy's with GFCI's, are there metal "Decora" covers available for handy boxes? I haven't been able to find them, and the plastic covers don't fit well on a handy box.

That sounds right. If you solder a ground wire onto it and bond it to the ground wire in the box, that ought to be okay. A lot of work...

I would have to agree with Sparky, don't use a metal cover on a plastic box.

I would say that the plastic over the metal any day. safer,more economical, and non conductive.

Of course there are other factors that you would have to consider in metal over plastic, durability ect........

Wayne

I'm with sparky on the plastic box issue. In residential applications, I like the hard plastic type because I think they look better than nylon. As far as steel plates are concerned, I like them in almost all commercial applications. Device cover plates that are UL listed have been tested, and are perfectly acceptable by the NEC.