Copper is, aside from silver, by far the most conductive metal. If copper is 100 on the conductivity scale aluminum is like 57 and gold about the same as aluminum. Pure copper soldering lugs are going to be the best by a long shot, other than them tarnishing. Gold doesn't really tarnish or corrode so if it's going to be exposed to the elements then gold plating would be helpful.
About the terminal you bought, just see what they are made out of to tell whether or not they are good. Really the metal is all that matters, everything else is just marketing.