OK,its a zombie thread.
It would be good to compare single stack to single stack,or double stack to double stack.
Standard 1911 single stack originally was a 7 rd 45 and a 9 rd 9mm.
A 45 ACP Shield is,what? 7 +1 vs 9mm 8+11? I'm not sure about that,I'd have to look it up.
Double stack 45 acp's are available,among them the RIA,Kimber..