Silver is very slightly lower, 1.6. Gold is a bit higher, 2.4. Silver and gold are different from copper in other ways than resistivity. Gold does not oxidize in normal environments, so gold contacts will not need periodic cleaning and will not create rectifying junctions. Silver will oxidize, but the oxide of silver is conductive, so oxidized silver will still make good contact.
Copper oxide is a bad conductor.
Oxidized copper contacts may insulate, may conduct, or may rectify. Copper is a bad material for cable terminals, but this may or may not mean anything for the conductor itself. First, a few words on terminology. Wire is sized by AWG or BS gauge number. Larger numbers represent smaller wire.