These are not REALLY electronic ignition systems, they are points replacement units.
Why change from "points" to
have a number of downsides, these primarily being that the points act as a
mechanical and electrical switch which over a period of time need re-setting
as the electrical spark erodes the contact surface. Also, the plastic heel
strip wears in contact with the distributor cam making the gap close up.
When the points begin to wear, the efficiency of the system is thrown out
and the engine begins to misfire, usually at the lower end of the rev'
range. The only solution is to remove, clean and reset or change the points
which on a VW air cooled engine is not very easy to complete. The second
problem associated with points is "bounce", which usually occurs at high
engine speeds were the points cannot physically remain in contact with the
distributor cam and "bounce", meaning that the points gap is not constant.
This is not usually a problem on VW engines due to the slow speed.
Benefits of Electronic ignition