I like the HEI a lot because it does not require a ballast and is a lot cheaper than a CD ignition. If I were to buy a CD type box, it would be a Crane as I had a lot of problems with MSD back in the '90's and old feelings die hard
The HEI has a variable dwell in the module which allows you to avoid the ballast.
The module should not be particularly rpm limited as long as you avoid the GM coil that came with them.
Once we were running a Falcon in a vintage class and the Ford ignition would start acting up before we got to 6000 rpm on the front straight away at Texas World Speedway. We switched to an HEI and matching coil and we starting seeing it flatten out about 6000 rpm. One of the crew was an EE and he put it on the scope and said the module was not the culprit. We then tried a Crane PS91 and were at 7200 at the braking point without a falter. I have seen more comments in recent years blaming it on the coil rather than the module.
Since then, I have tried it on other cars without a problem so when the box on my Challenger started acting up, I swapped to the HEI module and the Crane coil and it has worked like a charm. Car is a 440 with the Lunati 603 cam so it is not exactly a high rpm engine so I cannot say if it will turn 7000 or not...
The original GM four prong module was current limited to about 5 amps...some of the aftermarket modules like the Accel show a rating of about 7 amps as I recall.
I suspect a lot of the magic boxes out there today have a GM module under the potting compound. If they use a ballast resistor, it just seems stone age to me.
It is very important to use a good heat sink under the module with a dab of the proper grease under the module for good heat transfer and be sure the module is well grounded and in the air stream if possible. I guess it happens but I have never seen one fail when installed properly. I also always hot wire the module straight to the battery with a relay to activate it. This may be over kill but that's the way we built race cars and I just continue to do it.