Wrong, an engine can tolerate more advance at idle and light cruise.With manifold vacuum when you open the throttle the vacuum drops out and mechanical takes over.
Switch and tell me what feels better.
Also if you read most of these articles they switched to ported after emissions started in the early seventys. You might think too much adv. at idle but not so.
Depends on the vehicle "when they switched." The thing is if you are going to use manifold vacuum, YOU NEED a completely different distributor curve than for ported. I don't like, and have never used manifold vacuum