Some prefer the small primer 45 because they don't have to change their priming system from small to large when you reload multi calibers on a progressive press + only one primer to carry. Personally I prefer large primer 45, I find it seats better. Both work, I've reloaded both ways. One advantage is that with small rifle primers you could potentially reload everything pistol from 9mm to 45ACP (small primer) and 223, less inventory...if not one goes nuts between LP reg, LP magnum, SP reg, SP magnum, SR, LR reg, LR magnum, not to mention Benchrest grade and shotgun primers...not sure I got all the nomenclature right but you get my drift.