Rick,
Overall you post was right on. Pertronix now makes an Igniter III I believe it's called. It has rev limiter and muti-spark all in the module without the need for a box. There are cases for using manifold vacuum for the vacuum advance such as with a real radical cam. It can smooth out the idle and overcome carb idle issues. The other argument for using vacuum advance is race engines would have no use for it since they are running wide open most of the time. The vacuum advance would not even work. Most cobras are used on the street and could benefit from vacuum advance. Good Post Rick!
Wayne