What are the strengths and weaknesses of federal systems and centralized governments?

Many countries of the world have unitary systems of government.  In this system, the central government has all the power and only gives lower governments (states, provinces, prefectures, or others) whatever power it wishes to give.  The major strength of this kind of government is that it is more efficient than a federal system.  If the national government, for example, wants to implement a system of health care, it does not have state governments suing it, trying to prevent it from doing so.  The national government can do what it wants without having to deal with resistance from the lower levels of government.  The other important strength of this sort of government is that it is more consistent.  When the national government makes all the rules, the rules are the same for people everywhere.  In a federal system, you might have (as the US does) the death penalty in one state but not in another.  You might have abortion be harder to get in one state than another.  Not all citizens of the country enjoy the same rights in a federal system, but they do in a unitary system.

The United States has a federal system.  In this system, the Constitution spells out what powers the national government has and what powers the state governments have.  Neither level of government can simply take powers from the other level.  The most important strength of this system of government is that it allows different parts of a country to feel that they have more self-government.  This is particularly important in a big country, like the US, and/or in countries where different regions are very different.  It is important for people in a conservative place like Utah to feel that they do not have to have the exact same laws as people in a liberal place like New York City.  In a unitary system, all would have to follow the same laws, leading to more bitterness and resentment among people whose opinions lost out.  The other main strength of this system is that it allows different state governments to try different things.  In a unitary system, the whole country does the same thing so it is hard to determine if there is a better way to do that thing.  In a federal system, each state can do things differently.  People can then study the different approaches (for example, different ways to fund education) and can determine which method is the best.  This sort of “laboratory of democracy” is not available in a unitary system.

Both of these systems have their strengths and weaknesses, which is why it is hard to know which type of government is best.