If I read your source correctly, there is no real advantage of 60 Hertz or 50 Hertz, and the decision was usually due to circumstantial reasons, like supporting some existing arc-lights or difficulties with induction motors. Induction motors are also the reason why some railways chose to use 16⅔ Hertz, still in use to this day.

In the end, there is no real difference between 50 or 60 Hz, there is no clear advantage to either, especially with modern components. But you do have to choose as the whole network is synchronous.