I agree with this reader on the superiority of “Hardy” but I would assume NR would reject his method. Proper usage shouldn’t be a popularity contest. Of course, I am not an absolutist myself on such issues. Anyway, from a reader:
When I want to see which of two variants of something is more
widespread, I just google each phrase and see which has more hits. In
this case, Party Hearty has a slight lead over Party Hardy. It should,
because it makes more sense. Party Hardy seems more fitting for, say, an
outdoor party in the Arctic.