Several years ago when this was a hot topic, I did my own test. I have 3 favorite loads for my 45 ACP and tried some of the 3 half with small primers and half with large primers. My loads were 200 gr. LSWC over Bullseye, 230 gr. FMJ over Bullseye, and a cast 230 gr. TC over Universal. Long story short; Shot all in the same 1911, shot over my chrony on clear sunny days, and not enough difference to make a difference. So, it boils down to personal choice. Some won't accept anything except the "traditional" l large primers, some progressive press users find it difficult to swap priming tools on their press (or don't/won't inspect their brass prior to reloading.), some have used large primed 45 ACP brass for decades and are fine with what they have. I now have at least 300 small primed 45 ACP cases and several hundred (thousand?) large primed cases so i prime off my press with whatever primers I have the most of at the time...