One of the main features of most federal governments are two autonomous levels of government, which means that both federal level of government and the state level possess a variety of powers that the other cannot intrude on. A written constitution is also a main feature of a federal government, this makes sure that the different levels of government know their responsibilities and powers. This also means that both levels know that neither are able to amend the constitution on their own.
The main features of most unitary governments are a single central all-powerful government which means that all the power of the electorate lies within the hands of one single government. Typically the central government delegates powers to the counties but with strict control and supervision as is seen in the UK. Another feature of a typical unitary state is that it has a flexible constitution, a positive of this is that the constitution can be changed according to changing circumstances. A unitary state can have both a written or unwritten constitution.
I personally do not think that the distinction between federal and unitary states is still valid, because there are different varieties of federalism and unitary states. Administrative federalism is where the central government is the main policy maker and the state/provincial government has the responsibility of implementing the policies in their province, an example of this is in Austria and Germany. I feel as though this system of federalism is similar to the unitary system because technically the main power still lies with the central government and they are the body that delegates to the provinces/states. Another form of federalism is dual federalism, this was the US system of federalism. Dual federalism is where the federal and state government operate separately, so you’d typically find clear differences between the state and the federal government’s powers, functions and responsibilities. The US recently has been moving more towards cooperative federalism, this is where the central government has been increasingly taking the states powers by passing laws that prevent and restrict their powers. You could also argue that this variety of federalism is similar to unitary state system.
A good example of a unitary state which we could consider a federalist state would be Spain, as Spain’s system is known as a quasi-federal state, but is still known to be a unitary state. Spain is composed of 17 autonomous communities and two autonomous cities with varying degrees of autonomy under the Constitution, which nevertheless explicitly states the indivisible unity of the Spanish nation.
Central government, has progressively and asymmetrically devolved or transferred power and competences to the autonomous communities
The powers of central government have expanded, largely as a result of growth of economic and social intervention, and central government’s own greater revenue-raising capacities