Originally Posted by OneBadPig
I have been wondering if a polymer lower would be better(or not) with a piston upper.
I don't think they would be any better or worse than a metal lower. Polymer lowers are, in general, just less expensive to manufacture, but don't offer much of a difference when it comes to pros and cons for certain builds besides lower cost and slight weight savings.
For an AR pistol, I'd absolutely recommend one due to the few ounces you'd lose. For a piston build, I don't think you would see much benefit or negative in using one.