Altenators are lighter, more efficent, and more dependable. If you're going for a true restore though, I believe a 69 bug would have a generator.
Generator runs brushes and when they wear down, you are only running on the battery juice. I can't remember but I believe the bug runs off the battery and the gen charges it as with an alternator you can pull the battery when the bug is running and it will still run.
Generator - brushes, commutator converts to dc output, old school, good only for exact restoration.
Alternator - brushless, diodes converts ac to dc power, much better than generator.
Kind of like points distributor vs electronic ignition, an 009 is the top of the line points distributor for a VW, any electronic distributor is way better and lot less maintenance.
My 66 had the brushes worn down enough that I was running on battery power and that was going to crap. I was coming home from the valley from working nights and by the time I was almost home, I would have to turn off the lights to get more juice from the batt or my car would start misfiring. Popped in some new brushes the next day and BLAM! Al was good again.I have the same thing going through my head. To change over to the Alt I have to buy the stand, strap and change a little wireing. Should I or should I stay stock? I have NEVER had a problem with my genny and she is still in great condition. This is where I have been stuck and have not put the finishin touches to the motor on my bus.