I think the main reason people are shying away from the MP stuff is quality control. 30 years ago, it was top notch. Over time everything has been outsourced (not always a bad thing) and cheaper materials are being used so there are more failures. I think in comparison the GM HEI system is fewer pieces and provides just as good if not better spark.
All that said, I've been a big fan of the Mopar system for a long time. When working properly, it's hard to beat. With the blue, orange, chrome and gold boxes, there's an ignition system for pretty much whatever you want to do. But you can only carry SO many spare parts along for the ride. lol