Contrast a federal system at government …

In a federal form of government, the central government shares its powers with the various constituent units of the country. For example, in India, power is divided between the government at the Centre and the various State governments. In a unitary form of government, all the power is exercised by only one government.

Difference: 

(i) Unitary government has only one level of government whereas a federal government has two or more levels of government. 

(ii) In unitary government, the sub-units are subordinate to the centre, whereas in a federation, central government cannot encroach on the rights of state governments. 

(iii) In unitary system, centre can order the sub-units which cannot happen in federation. 

A federation is preferred because: 

(i) It helps in making administration effective and efficient. 

(ii) It helps to accommodate all diverse groups.