Well, Gold does cost the manufacturer more than silver, or tin.Methinks you are right about the "Silver" being "Tin".Silver is an excellent conductor of electricity, but it corrodes easily.Gold,OTOH,does not.
Anytime you mix two different metals together (touching)you get an electrolytic action....that's what happens inside a battery.One or both of the differing metals gets eaten away,converted to some other substance.
Electrically,gold and tin should not be much of a problem, unless you have a fair amount of moisture over a long period of time.
Stainless steel can normally be used between two differing metals, it is almost completely inert to the electrolytic effect.
Go for the Gold.