Do pure copper banana plugs make a difference in the quality of the speaker sound.

That KLE style banana is what DNM uses. Pretty secure. But the receiving banana hole has to fit really well too.

@redwoodaudio - you are correct.

Fortunately - you can "adjust" the KLE Bananas quite easily.

I use an old banana plug similar to this one...
https://www.amazon.ca/GearIT-Premium-Braided-Speaker-Plated/dp/B0713ZDBM2/ref=redir_mobile_desktop?i...

I removed that little piece of wire on the pin. The shaft of this banana then fits nicely inside of the KLE Banana, making them expand ever so slightly to allow them to fit "Snuggly" in most binding posts.

But as I said, they are more delicate than many other alternatives, but they sound great

Regards - Steve

  The correct answer is what you like based on your system in your house . Beware of the people that tell you what you will hear in  “Absolute statements “. I use some bananas and some spades . For me in my system , silver on the connectors or in/on the wires ads a brightness to my system in my listening room that I don’t care for . If you are fortunate enough to have friends that will lend you cables to try , take advantage of it . I personally don’t believe in the NASA based article that “ wire is wire “. But I have a budget on the modest side and don’t run high priced wire . I’ve had good luck at my price point with Anti Cables , Morrow , Cardas, and Audioquest. I’ve experienced noticeable improvement with break in too . Morrow interconnects take 400 hours . I also believe in cleaning and treating my connections. This is one of the many experiences we get to enjoy building  our systems . If this doesn’t drive you crazy, explore tube rolling . Best wishes and happy hunting . 

Rhodium is the best material for contact surfaces. It is harder than gold. Rhodium is a good conductor (although this is not important for contacts), and rhodium does not tarnish. Second is gold, since it doesn’t tarnish as much as other materials. All military connectors use gold. Rhodium is too expensive. But gold is soft and not a great conductor compared to copper or silver; so it is generally a poor choice for the wire itself. Silver is the best conductor for wire.

Btw, “white gold” jewelry is just rhodium plated gold.