2 Field Alternator Question

Just FYI... there aren't 2 fields. Every alternator has a single field with a positive wire and a ground wire. I must back up a bit and say welllll not exactly. The early design had a positive wire only. The field was chassis grounded just like most everything else on the car, so no actual ground wire. That voltage regulator modulated the positive side of the field. This is called closed field.
The later design is called isolated field. The regulator modulates the ground side of the field via the actual ground wire.
I suppose someone here could explain the advantages/disadvantages of both designs and why factory engineers made this change. When I changed from 36 amp round back to 60 amp square back alternator I figured I didn't need to be so enlightened. I could just follow the lead of the factory engineers and add approx' 8 feet of blue wire to my harness.