I'm gonna throw in with the World 1 folks - I really liked the generally smaller community and that pretty much everybody knew everybody. The day I log in to find scents - not long after they were implemented - on my steel crucibles and after an hour and a half or so of impotent tracking discovering it was fricking loftar peeking inside them is magic I will never forget. I think it's my bias that I felt the updates were more interesting - I remember setting out across the grasslands (this was the primary biome of World 1, instead of forest) in search of silkmoths, working with Vanigo to discover the secrets of cheese, etc., but I also remember the Symbel, rafts (and other frequent relatively minor things), the discussion around whatever-you-call-the-automated-pathing-things-I-don't-think-anyone-uses from World 3.
Also the constant talk of superplayers in World 1 like some sort of bogeyman (although Blaze was always helpful and Raephire was... well, Raephire)
I'm not sure where burg gets 'no fighting, no politics, no drama' - I doubt it was ever on the scale of a later world, but I remember being tangentially involved in discussions on raiding the goons and a couple of other little skirmishes. The world - and forums, for that matter - were generally more peaceful though, if only due to lower population and the abundance of pretty much everything except wood.
I feel like World 3 was probably the height of the game, though - still regular updates, most of the systems that defined the game in place, everybody seemed to be at the top of their game, etc. etc. My involvement in the politics was always pretty much 'floating around the exterior of whatever Bottleneck called themselves at the time', I'll admit. I barely remember World 4, although it's the only world I was around for the entirety of. World 5 was when the group we'd built up started to disintegrate and I drifted off again so I can't speak to it.
World 2 gets an honorable mention for funnest start for me, though, if only because it was unique for letting us bring our fully developed characters into it. (I remember following Blaze around for some reason on that first day, looking for... something.)