mbliss57 in my experience the main difference......and perhaps the most important difference, between 3rd gen 45's and 1911's, is reliability. Having initially trained on 1911's and carried one on duty for a short period of time, I can tell you that while there are a couple of brands of 1911's that will work right out of the box........most of the time - without any tinkering or smithing - the vast majority need to be extensively tested with different ammunition and even different magazines to insure reliability.
Other than insuring your carry ammo POA = POI, there are no such requirements for rigorous testing with 3rd gen 45's.
The only light weight, CCW, 1911 patern pistol I've ever seen approach the reliability of the S&W 3rd generation 45's was my old partners Colt Defender. It still occasionally choked. Probably because my old partner was not exactly OCD about maintenance and cleaning.
Personally, I feel that 1911's have a great historic value and are fine range toys. But if you are not inclined to pay lots of money to gunsmiths for making them reliable AND do regular rote maintenance and cleaning, as well as learning some basic gunsmithing skills, you would be better served by a 3rd generation 45 for use as a carry gun. I know I am.
Oh, avoid Kimber. Great looking, tack driving, single shot, rust prone, MIM filled, overpriced and overhyped 1911's.
Good luck! Regards 18DAI