Express is the worst server of the lot. Avoid Express.

It has special rules because of the overly-fast pace of turns (Commies can sell 65%), unnatural wars which won't happen on any other server due to the extreme amount of turns you can store and use at one go, and an insufficient number of mods to cover all time zones (by the time they respond, you are 600 turns behind, or the equivalent of 8-10 days of turns on every other server).

The Express experience is obviously different and unique (and a lot of people like it for that exact reason), but if you play it, don't expect the experience of playing strategies to carry over to any other server. It is that significantly different, and Express is not representative of any other solo server. Many feel it is a joke server because of the "throwaway" nature of the resets. Screw it up? Just wait 1 week and try again. Some also use it as a testbed for the first 100-200 turns and then abandon the country to test a startup for the other servers. Express server is only for the people with lots of time to micromanage their country every 1-2 hours, and that puts such players at an advantage over the ones that have no time to play that heavily.