For me base material matters the most, then coating mix.
I always find that pure copper as base material and silver/rhodium plating as coating works great.
What is best, depends on your system, whether you want to push things, mellow or refine.
My preference is for silver plated copper - it provides better transmisson/clarity and faster dynamics
The tarnish does not bother me because
I am happy with my sound and see no advantage in obsessing over tarnish, because most of the connctors seldon tarnish in the atmosphere of my home
I have tried other types of metals and platings and prefer dynamics and clarity of the silver plated Copper
Regards - Steve