Some of the advantages of federal government is the fact that it practices pragmatism, which helps states and local officials fix the problems in their direct area. Federalism prevents tyranny and ensures the separation of powers. State governments will still function independently, even if one person took control of all three branches of the federal government. But through all of this, it leads to a lack of accountability. Overlapping of boundaries among national and state governments make it tricky ot assign blame for failed policies.
Some of the advantages of the confederate governments is that it keeps the power at local levels. This prevents the growth of a large central government.