Read somewhere here that someone said each world was basically the same. This is not so.
World 3 was very comparable to the world during the cold war. You had this massive build up of resources and troops for months, yet all out war never really took place. So it was pretty peaceful although, just like the cold war, tensions went up at intervals (battle of BHB?) and other 'incidents'.
Then you had World 4 which was pretty awesome imo, I didn't play a lot then, but reading the bottleneck threads was great. This was the last world I played on. It was kind of more like W2 because it was not at all like W3 (which was pretty peaceful).
The thing about Haven and Hearth is that there are so many great stories. You could write an entire book about World 3 politics, territories, incidents and the like.
edit/
Just think about it, in W3 there were even public and private markets, Constantinople up to a certain level, and then the Buyan private market.