While he's not my personal favorite, I think Julian embodies the smug persona best. He's a flamboyant unicorn in a house that's totally extra, doesn't get more smug than that!
the peak of my activity in the forums was in new leaf where marshal was too popular—even i'd say he was overhyped. though i definitely think he's become the figurehead of the smug personality that stands the test of time. raymond, i think, came about in a bad timing where the game became mainstream and commodified, so there's this bandwagon/polarity of adoration and hate.
tldr - i personally say marshal because it's so comical for a tiny squirrel to be so smug. julian second, maybe zell third.
(i also never thought pietro was smug)
Marshal of course is the number one smug to me! I also voted for Julian since I think he fits the new smug personality extremely well. Raymond is nice, but I some how don't feel like smug is the best personality for him