They are all fine pistols, hard to go wrong with any of them.
I have had very positive experiences with Ruger pistols in other than .45 SS models...I do not own a Ruger semi auto .45. I have a Colt Commander (my Dad's gun from Korea and Vietnam) and a Kimber.
That said, if I was looking, hard to argue:
Ruger SR1911CMD 45 ACP Stainless Semi-Automatic Pistol