Go with RAD 9 since threaded barrel I have is 9mm or RAD 45 for future versatility? I don't foresee getting a threaded .40 or .45 barrel soon. My understanding is you can shoot sub 300 BLK through RAD 45 (don't think it would/should be a regular thing to do). Not sure about RAD and sub 300 BLK.
How much 9mm precision is lost with RAD 45?