You should be able to figure it out by looking at how your system is wired. If the ballast resistor is just dropping the voltage to the MSD ignition box then it is hurting your performance and it probably isn't extending the life of the MSD box. The ballast resistor was originally designed to protect the points. It was then repurposed in the ECU era to protect the life of the coil. Look at how the last guy wired the ignition in your car. Does the coil get its voltage from the ballast resistor or is it coming from the MSD box?
You have to actually study how the system before you'll know what the last guy did. He might have bypassed the ballast but just left it there or perhaps he didn't read the instructions and he actually wired it up so the MSD box isn't receiving a full 12 volts. Anything is possible when dealing with backyard mechanics.