What difference/s are there between SVDA and 009 distributors ?

SVDA has vacuum advance to help pick up from low revs useful on hills as it make the engine pick up better than just throwing more fuel in. 009 was for industrial engines running at high rpm which is why they were favoured by folks on racing circuits

009 was also used by Porsche on various models, SVDA is designed to work of a single carb.

 VW used centrifugal only distributors on a lot of models as well as SVDA, Dual VDA and we expect one or two generic distributors to fit all some of them are emissions based changes.
https://www.airschooled.com/distributor-parts-specifications

Thanks guys