If you compare these two types of screeds, then concrete has some advantages over cement. For example, it is not so wet, since the water in the concrete solution is much smaller, and when using a concrete screed one can not be afraid of flowing to the lower floors. In addition, the concrete screed gives less shrinkage.
Of course, the concrete screed can be manufactured independently, but there is a great risk that some mistakes will be made in the process, which in the future will negatively affect the quality of the flooring. No matter how, and the process of pouring concrete screed is very complicated.