Packing and Shipping:
The disadvantages of plastic boxes
The disadvantages of plastic boxes are their brittleness and wire support brackets.
Let me explain. If you look at the box, you'll notice that the device screw holes are also plastic. If the screw is lined up when installing the device, you're fine. But get the screw cross-threaded and you have a problem. Suddenly the screw won't tighten down and the device is flopping in the wind. If the metal hole in a metal box strips out, you can just tap it out and it's as good as new.