Small primer .45 ACP are really popular here among reloaders in Canada, and they cost a lot more due to them still being more rare and having to be sorted out. No significant ballistic difference from those who use them that I know of. But reloaders who also load other calibers that take small primer such as 9mm love them because you don't have to switch over the priming system of your press when changing calibers. Believe me, this is a huge thing among us Dillon XL 650 users. The only Dillion 650 owners that I personally know of that load 9mm and conventional large primer .45 ACP have two presses!
I use my Lee Classic Turret press to load .45 ACP with large primers, and my Dillion XL 650 is dedicated to 9mm. This makes life much easier