All plastics are polymers but not all polymers are plastics.Polymer is stronger than plastic but not as strong as steel.
So SOME polymers are stronger than the strongest plastic, but it's not a given that polymer is stronger than plastic because any plastic you choose to talk about is a polymer and obviously that polymer can't be stronger than itself.
The guide rods are solid plastic. The other parts are rough metal parts with a molded plastic overlay. There don't seem to be many complaints about the parts from a functional standpoint, most people just object to the general idea.So is it plastic coated metal or just plastic parts?
Good things. They don't rust, they are easier on the hands when the gun gets very hot or the temperature is very cold. They help the manufacturer make a profit. The finish doesn't wear off.
Bad things. They look bad on stainless guns. They don't work with some aftermarket accessories. They're probably not quite as strong as the all-metal parts.