Disadvantages of Federalism
It can lead to duplication of government and inefficient, over-lapping or contradictory policies in different parts of the country. The most famous example of this was the different railway gauges in the States that was an issue during the Federation debates of the 1890s. In more recent times, each State has its own education system with differing curriculums and assessment methods.
It can lead to inequality between the States and lead to unhealthy competition and rivalry between them. This has been seen in recent years with States "stealing" major sporting events from each other, and in differences in the availability and cost of electricity between the States.
It can lead to neglect in important areas of public policy. This can be seen in the decline of the Murrary River system, particularly the problem of salinity. A solution depends on co-operation between the governments of South Australia, Victoria, New South Wales and the Commonwealth. Probems with public transport are often cited as an area of neglect.
It can lead to over-government. It is often argued that a nation of 19 million people cannot afford to have 15 houses of parliament, plus hundreds of local governments.