We were out shooting some 9mm Sterling SMGs with the local Sheriff's Dept., who were issued .45 HK UMPs at the time. They had hauled out some old vehicles to practice upon, so we took turns perforating them to see what happened to the targets behind and inside. Turns out the 9mms were rather better at reaching the "bad guys"! Very few of the .45 rounds would get through more than one layer of sheet metal, glass, or what have you, whilst the 9s would regularly get through the whole thing. Was surprising to all of us.

As for the .45 ACP as a carry round, I do so fairly often. Or a 9mm. But usually it's .38+ for me.

It does seem easier to get good bull's eye accuracy out to 50 yds. with the .45 ACP than most other auto pistol rounds. Again, YMMV.