I have heard of all sorts of theories too, between copper stainless and even glass. It all seem like personal preference, like Ford or Chevy, but one thing seems to stand fast in all of my ,what is loosley described as, research.
Just about all, recommend some sort of copper packing or mash, in the reflux column. This not only gives alot of surface area for reflux, it is believed to aid with some sort of chemical reaction between the raw alcohol vapor, removing or neutralizing negative things ,either ions or odor or something like that,. I also heard that glass is too thermal resistant and does not as easily cool in the condensing worm as it does in copper or stainless. Also breakable.

Copper removes sulfur compounds, such as hydrogen sulfide. The copper reacts with sulfurs and turns black. The result is a cleaner sweeter tasting and smelling distillate. If you use raschig rings for packing, try adding one chore-boy copper scrub pad to the column packing. I think you'll be peased with the results.