The advantages of a communist system is that everyone, theoretically at least, has what they need to live, and contributes what they can to the common good. There are no vast disparities of wealth and poverty (again in theory) and resources are allocated to those who need them most.
The disadvantage of a communist system is that it relies upon everyone in the system being altruistic. It does not take into account that people tend to be selfish, and do what is in their personal best interests.
The communist system in reality was subject to gamesmanship on all levels, from the individual worker up to the party boss. Another fault of the communist system is that it relies on centralized planners to send manufacturing signals. Any centralized planning system cannot respond to changes in demand as rapidly as needed, and so some goods are overproduced, while others are underproduced. And due to the lack of individual incentive to produce, there is less in the aggregate for everyone.
Probably the greatest disadvantage ever of Communism was Mau Tsi Tung....he murdered millions.
42 mths ago