<In a federal state, a region can be conservatively governed while its neighbour can be liberally governed; one region will prosper faster than the other and that way comparative studies can be made. It's as I said, a matter of distributing competences.

You are right, and this would indeed be a good way to set it up. Ideally, this was how the U.S. was originally supposed to be set up, with very limited powers granted by the Constitution to the Federal government.

The Tenth Amendment to the Constitution:



The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.



A very powerful statement. Means that unless the Constitution says so, the Federal government can't do it. Unless the Constitution says the states and the people can't do it, they are free--as far as the Federal government is concerned--to do what they want. Limits on the State, and few if any on the citizens.

This one used to actually mean something. It's pretty much toilet paper now, ravaged by years of "interpretations." In practice, today the U.S. Federal government is pretty much all-powerful, and state government is kind of an appendage to the whole process. Never mind local government.

I don't see anything different happening to a European Federation--the growth of a central authority beyond all reason.