There's something like 8 different formulations of neversieze that I found in McMaster Carr catalog.... copper, nickel, aluminum, moly disulfide, graphite, teflon, etc. Nickel is for very high temp applications. Copper is for high temp and general applications. It doesn't make a whole lot of difference which kind you get. Their primary function is all the same. I think the copper stuff is most widely sold, though it appears grey and Permatex doesn't specifically list the formulation on the bottle.
95 E320 Cabriolet, 131K