What are the advantages and disadvantages of a unicellular organism in comparison with multicellular organisms?

The main advantage of a unicellular organism is its structure. These are primitive organisms that perform all the basic functions of life within one cage. If in a multicellular organism each individual cell specializes in one thing, specific and cannot perform the functions of other cells, then in a unicellular organism this cell can perform all the functions of a multicellular organism. They breathe, and multiply, and feed, and grow. Thus, unicellular organisms are universal: if in a multicellular organism any one cell stops performing its function, this will affect the whole organism. But at the same time. unicellular organisms are very primitive.