Efficiency can mean different things in different contexts. But in general, the efficiency of an electric power system is determined by many factors, including the design and operation of the generation, transmission, and distribution systems, as well as the energy conversion efficiencies of the equipment used in the system, such as transformers and motors.
In terms of the frequency of the AC power, 50Hz and 60Hz are both commonly used frequencies around the world and both are equally efficient in terms of the energy conversion process. The choice of frequency is typically determined by regional standards and historical considerations, and is not necessarily related to efficiency. For example, in Europe and many countries in Africa, Asia, and South America, the standard frequency is 50Hz, while in North America, most of Central and South America, and some parts of the Caribbean, the standard frequency is 60Hz.
Ultimately, the efficiency of an electric power system depends on a multitude of factors and the choice of frequency is just one of them.
