This is, of course, a matter of opinion. There is no objective way to choose whether federalism is better than some other system. Let us look at some arguments for and against federalism.
There are a few main arguments for federalism. They include:
The state governments are closer to the people and more likely to do what the people want. The idea here is that the federal government is distant from most states and does not really care as much about a given state as the people of that state do. Therefore, state governments are more likely to do what is best for a state.
Different states are too different and cannot really be expected to have the same laws. For example, a state like Texas needs to be allowed to have the death penalty because that is what its people want, but a state like New York should be able to ban it since its people are much more liberal.
States are laboratories for different policies. Since states can have different policies, we have the chance to try out different things and see what works.
The main argument for giving more power to the federal government is that it is simply wrong for different Americans to have different rights. It is wrong for a woman in one state to have the right to an abortion while a woman in the next state does not. (Or, if you want to look at it this way, it is wrong for a fetus in one state to be protected while a fetus in the next state is not.) We are all Americans and we should all have the same rights.