The Cruel Desert map was made for multyplayer, so I was tending to make a balanced map: all are able to build 2 iron mines and 2 stone quarries, while it is not a typical multiplayer map: I don't like geometrically exact maps - I don't find it interesting, and this is the reason of making such a map. I hope you'll like it! :)
Other five maps: some I made myself, while some of them made my mother! :P They are designed for singleplayer games, and that's why there are more resources.
Of course, that is only an introduce, they can all be played in multiplayer and singleplayer.