If there is an abundance of resources and money as on the easier difficulty levels, the differences in built-up requirements for the different towns are obscured, although those differences are clearly part of the overall balancing of towns. For instance, it is rather obvious, that Dungeon has a great line-up with 3 flyers (6th and 7th level creatures included), 2 medium shooters and 2 grunts. Getting all creature structures on impossible difficulty is another matter. The Pillar of Eyes which gives Dungeon its 3rd level creature is a prerequisite for every creature dwelling thereafter. To build the Pillar of Eyes you need 1000 gold and 1 each of the six resources. On easier difficulties it is no problem to build this structure. On impossible difficulty you may find it impossible to build that structure in the first week, because with only a bit of bad luck you simply may not find a stack of every resource.
Also, Salamandre, you mentioned that in the middle of week one you could send out several scout-hooligan heroes to the enemy territory to pick up goodies in the Tournament of Honor. What difficulty were these games played on ?