Totally depends on timeline and if we’re also including TLoK as well. Anytime before the wars began, gotta agree with someone else who said fire nation. During the war? Probably still in the fire nation since you don’t really see them getting attacked in their nation much. The fascist kinda lifestyle wouldn’t be too cool, but would rather not live in constant fear of being attacked over accidentally saying something wrong. Especially since I’m fairly positive there’s no way I’d be a bender.
If we’re talking TLoK included, don’t remember which natition it’s in, but the metal city where they literally open it up like a blooming flower seems like a cool place to live.