Hey Falkirk,
This debate has taken place a number of times, so, it would be worth while to look through prior posts on the subject. As an example the following is a copy of a post I submitted to a forum question ..."Duraspark vs. Pertronix"...
..."You have asked a question that could set off quite a debate, DuraSpark vs. Pertronix. I favor the Pertronix II because the technology is newer, the performance is excellent, and reliability is better (I'm it trouble now).
Reliability. While this comment is second hand, I will say that I have not met a Ford machanic who hasn't said that the DSII "box" is unreliable. As a matter of fact, I had one tell me they made it a policy ..."back then"... to keep several on hand because they had to switch them out so often. As for Pertronix, they DO NOT perform well without a 12 volt hook-up. So, there a are lot of Ford owners out there who did not have a good experience with the Pertronix system. Why? Based on a response to an MCA letter, which response was published by MCA on their sight, Pertronix determined that there installation instructions were not clear. As a result, many of the users reporting poor performance had powered the unit via direct hook up to the distriubtor, which is NOT a 12 volt switched source. This problem was solved with the Pertronix II.
Technology. The Pertronix and the DSII are more than 25 years old. In the case of the DSII, it has not been used since the advent of fuel injection (mid 80's). The original Pertronix unit is more than 25 years old. This not to say that they don't work, or that you will not have good luck with them.
Pertronix II with Flamethrower 2. About two years old. Upgrade 1 - converts coil to 12 volt by eliminating the ballast resistor in the coil circuit (this is a good thing). Upgrade 2 - the system has built in dwell control. This helps to insure maximum spark signal throughout the RPM range (one would have to add MSD to the DSII, at a cost of $150+, to get this function). Upgrade 3 - the system has a built in circuit protector to prevent burning up the module if the key is left on while the engine is not running, i.e., if you set and listen to your sound system.
Bottom line, for $115 you get a 12 volt system with a 45,000 volt spark and dwell control. As a side benefit, this unit can be installed in about 20 minutes (easier than replacing points).
As a final note, the fact that you want to upgrage your dual vac distributor begs another question / comment. What are your long range plans for the car? Specifically, do you plan to add a performance carburetor? This is an important consideration because (and I learned this lesson the hard way), NONE of the typical / popular performance carbs (Holley or Weber) support the dual vac dizzy, and the Pertronix unit that fits the dual vac probably will not fit the single vac dizzy required with these carbs. So, if you invision a carb change somewhere down the road you may want to upgrade the the dizzy when you do the Pertronix II. This way you'll be ready for any carb change you may want to make, including one that would require a mechanical only set up as the single vac unit is easily converted."...
The total cost of the PII with Flamethrower II is $115 at Mustangs Unlimited. A rebuilt dual advance dizzy is $65 same place.
For some more insight into this issue take a look at "distrbutor help" on this same forum page.
Enjoy the trip - Steve