53........
120/208 is used mostly because of not only having the luxury of 3 phase for motor applications, but it also avails you to 3 seperate 120 volt circuits from the transformer secondary. If you are using 120/240, you would only have two, because it is a center-tapped single phase. Thanks to the connection of the "grounded" conductor, which would be your common on your three phase "wye" secondary, you have the opportunity for more circuits on a much more balanced load. The more balanced the load, the less you are asking of your neutral. Hope this helps.