Round back uses individual diodes that must be pressed out and back in and you had to do a lot of soldering to rebuild them. The square back had an easily replaceable diode pack and no soldering required. The one and two wire distinction is only because on the round back the second wire was simply grounded directly at the case where on the square back the new electronic regulator they wanted in the ground end of the alternator so they did not ground it but put a terminal so it could be run to the regulator to allow that to ground it to control regulation. The physics of the two are the same, just a different implementation. Any better functionally is because of pulley configurations to spin it faster or changes in the number of turns in the field or stator windings, not really inherent to the difference between the two implementations.
