Ignition wiring question

In tidying up some engine compartment wiring (see photo below for the rather ratty "before" state), in the short run to the coils/engine sensors I found two larger gauge (12?) red wires folded back and taped over, unused. To the + side of the coils is one larger yellow wire to one coil, with a jumper wire to the other + terminal. The additional black and red wires in the photo lower left are for the Pertronix dual trigger unit which was fitted at time of purchase last year. I've been running a 123+ electronic ignition with non ballasted Bosch coils since then, utilizing only the +12v yellow wire as I was unaware of the other red wire options.

This clearly does not match the factory wiring diagram which has the two red wires going one to each coil and the yellow attached to one side of the resistor on each coil (with jumper).

So two questions:
What was the purpose of the factory 3 wire arrangement to the coils?

And, which wires to use? I'm thinking I should be using the red wires as they are fed by the ignition relay, while the yellow wire is directly key switched hot if I'm reading the diagram correctly.



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Thanks for all the responses

After more study of the wiring diagram, the yellow wire would be the correct choice to use if not using ballasted coils. The red wires are only 'hot' when the starter is energized, providing a full 12 volts to the coils, bypassing the ballast resistors.

 

Thanks, Steve!