On a car i used to have, an extra hot coil prematurely killed a hidden-in-distributor perktronix module. bought the right coil, and new module and it ran 100% perfect with no timing adjustment. awesome first hand experience. this was a 275hp SBF that didn't need a large ignition controller.

for people with crank triggers or magnetos, msd might have better integration

msd bragged for years about multi-spark feature. then (perktronix) second strike came out saying they're good well beyond 3000 rpm but others (like msd) are not. I recall summit putting second strike to a test, and had to report both msd and summit's in-house multi-spark box were inferior. they figured oh well, we make money selling perktronix too.