Argon vs nitrogen for preserving wine
In chemistry, some chemical species can still react with nitrogen so argon is usually favored, but, in the case of wines, none of the two should react whatsoever.

In both cases, however, the high density of argon is an advantage because it will always fall down to be in contact with the liquid in order to avoid contact with oxygen.

By contrast, nitrogen would just dilute oxygen in the remaining air and just slow down oxidation, because air is already composed of 80% nitrogen.