Found this on the web:
An alternator is more efficient at charging across much of the RPM range of the engine. It can produce a higher output at lower RPM by increasing the excitation in the field windings. At higher RPM, the output can be reduced by lowering the field excitation. This is done automatically and electronically by the alternator regulator circuitry.

With older vehicles, especially in winter or at night when you had the lights and heater on, the output from the generator at low RPM wasn’t enough to keep the battery charging properly to keep up with the demand.
Alternators also have slip rings which are much less prone to wear than the brushes and commutators of DC generators.

Also, alternator is more compact and most often contains the voltage regulator, which cleans up wiring.

Availability is more widespread if you happen to need a replacement too.

Last edited by sstock; 02/10/2019 1:42 PM.
1953 Chevrolet 3100
261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done
In the DITY Gallery
Video of the 261 running

1964 GMC 1000
305 Big Block V6, sm420, the next cab off restoration