Well, it keeps the parts guys in business. :wink:
The "Big" advantage is an alternator puts out a little more amps and the brushes last longer. Another "Big" advantage is the new alternators have solid state regulators that are pretty reliable. But, Bosch now makes a solid state regulator for generators. I put one on Homer about a year and half ago and ALL of my eletrical problems went away.
The biggest advantage of a generator, in my humble opinion, is that you can wire the generator up to run as a motor. If you break a belt, as long as you have a good charge on the battery you can keep the engine from melting down for a few miles. This can be a big deal if you're back in the woods in a Baja or on side of the interstate 5 miles from the nearest exit with no cell phone service.