With the Pertronix ignition and your stock coil, you are getting the same spark but in a much better controlled delivery.
If you do upgrade your coil, you could take advantage of the larger gap in plugs and thus improve your combustion. If you have a bigger spark, you get a more full detonation and better utilization of gas, air and chances are good to get complete combustion. A smaller spark does it well enough. The difference you get between small and large spark could make a real difference in your starting as well as performance.
You are really not taking advantage of the electronic ignition without the bigger coil, Pertronix or any other reputable brand.