It's not about conductivity, it's about reactivity. Most metals oxidise or tarnish when exposed to air/moisture, and that oxide layer is usually a really poor conductor compared to the original metal. Gold is extremely non-reactive, so no insulating layer forms on it and the end result is a connection that is *much* better than one with oxides in the middle.
That's definitely an issue with connectors generally. Silver oxide is reasonably conductive so for some connectors silver is preferred. Most high end RF connectors are silver - like BNC. A BNC connector ensures there is some wiping action when connecting and this helps displace the oxide to some degree.
On the other hand, I think the issue with edge connectors is more complex than just the connection materials. Other connector properties come into ply.
Edge connectors work perfectly in dust free environments even the old ones as that is where they came from before they ended up in the domestic environment. Vibration is also an issue in a dusty environment.
The old style edge socket had two contacts that were curved and flat in shape, flexed from the cable end and the two curved contacts were connected at the other end as well. This placed a curved shape gap on either side of the contact point so that any vibration would tend to draw dust closer to the center of the contact point and eventually break contact.
New edge connectors have round rather than flat contact surfaces and they are sprung from the opposite end and not connected at the floating end. They also have a different curved shape that is biased greatly to one side ... the inner side where there shouldn't be any dust.
So in a dust environment your only save is to remove dust by the wiping action of removing and re-inserting or blowing the dust out. This is where softer material do better because that have a greater contact surface area and are more malleable so they can absorb the very smallest dust particles.
