Much depends on the application.
For antenna use, for example, 2 critical factors
are frequency and antenna current.
As the radio
frequency increases, loss mechanisms of a surface
nature such as dielectric loss in surface contaminants
(such as oxides) are significant. Also the conductivity
loss becomes significant because it is a constant
per wavelength, and there will be a larger number
of wavelengths at higher frequencies. Copper has
a high bulk conductivity but copper oxide film on
the surface increases the surface resistance and
hence loss. Silver compounds form more slowly in
contact with air, except for silver sulfide. This
is the black tarnish seen on silver. However, its
conductivity is no too bad and only becomes significant
in really critical applications such as in some
high Q filters or first stage receiver circuits
where very low noise factors are needed.
with gold is then used for these very critical applications.
Where antenna currents are high, for example
high Q small loop antennas, conductivity is important
in order to ensure good efficiency and avoid heating
effects at high power. Where antenna current is
low, for example multiple element wideband structures
with high feed impedance, the material used is not
critical. I have used zinc galvanized steel at UHF
with no discernable deterioration compared to copper