Advantages of Centrally planned economy :
The government can harness land, labor, and capital to serve the economic objectives of the state (which, in turn, may be decided by a plurality of the people through a democratic process). Consumer demand can be restrained in favor of greater capital investment for economic development in a desired pattern. The state can begin building a heavy industry at once in an underdeveloped economy without waiting years for capital to accumulate through the expansion of light industry, and without reliance on external financing.
Consumers do not need money to express their economic demands; they may participate in democratic decision-making bodies (such as workers' councils or soviets) to voice their opinions and make decisions about the economy. 
A planned economy can serve social rather than individual needs: under such a system, rewards, whether wages or perquisites, are to be distributed according to the social value of the service performed. A planned economy eliminates the dependence of production on individual profit motives, which may not in themselves provide for all society's needs.
While a market economy maximises wealth by evolution, a planned economy favors design. While evolution tends to lead to a local maximum in aggregate wealth, design is in theory capable of achieving a global maximum. For example, a planned city can be designed for efficient transport, while organically grown cities tend to suffer from traffic congestion.
Taken as a whole, a centrally planned economy would attempt to substitute a number of firms with a single firm for an entire economy. As such, the stability of a planned economy has implications with the Theory of the firm. After all, most corporations are essentially 'centrally planned economies', aside from some token intra-corporate pricing (not to mention that the politics in some corporations resemble that of the Soviet Politburo). That is, corporations are essentially miniature centrally planned economies and seem to do just fine in a free market. As pointed out by Kenneth Arrow and others, the existence of firms in free markets shows that there is a need for firms in free markets; opponents of planned economies would simply argue that there is no need for a sole firm for the entire economy
Supporters of command economies argue that it enables the government to overcome market failure, inequality and create a society that maximises social welfare rather than maximises profit.
Command economies can prevent abuse of monopoly power.
Command economies can prevent mass unemployment, often a feature of capitalist economies.
Command economies could produce goods which benefit society and ensure everyone has access to basic necessities.
advantages is that you are guaranteed certain standard of life, as long as you are willing to work or meet your production quota. You get free education and healthcare, as well as disability and retirement benefits.
Prices are kept under control and thus everybody can afford to consume goods and services.
There is less inequality of wealth.
There is no duplication as the allocation of resources is centrally planned.
Low level of unemployment as the government aims to provide employment to everybody.
Elimination of waste resulting from competition between firms.
The advantages of a planned economy are that the high degree of control leads to a high level of stability in the system which means that an investor will not lose his money due to some sudden downturn and the changes are quite predictable. The entire system conforms to certain standard which means that everything is uniform which helps establish more control. In a planned economy, the individual efforts are directed towards a certain goalby the restrictions which mean that all the energy can be focused towardsachieving a specific economic and social goal of the government. It