As I understand it there has not been any new USGI M1911s produced since the end of WW2. Many have been rebuilt with parts replaced as needed, but the heat treating of the time was much inferior to what it is today. As such, the typical lifespan of a USGI M1911 is only about 20,000 rounds before major parts failure. The most common failure is a crack in the slide. 20,000 rounds sounds like a lot but it really isn't if you tend to shoot a lot.Springfield Armory, a very reputable private company, make several versions of the M1911, including a Mil-Spec version. I have a military version .45 ACP made by them over 20 years ago and a new manufactured "Ronin" in 10mm. Both are utterly reliable and required no after market accessories or gunsmith fiddling to get them to "run" flawlessly, and both are extremely well made and accurate.
1911 Mil-Spec Handguns - Springfield Armory
Between Springfield Inc. and Colt, I would probably choose Colt instead of Springfield. From the forums, Springfield seems to have really well meaning customer service but there have been way too many cases of the same pistol going back multiple times for the same problem.
The extractor seems to be a recurring theme in the forums.
As for Colt, They seem to be a known quantity though they are (in my opinion) a bit overpriced for what you actually get.
I disagree with you that the M1911 is a relatively uncomplicated design. It is uncomplicated in theory of operation, but the fitting and interaction of parts needed for smooth running are actually quite complicated. For good accuracy, there needs to be fairly tight lockup between barrel and slide lugs. The barrel hood needs to fit with minimal clearance side to side in the slide and NO clearance against the breech face. When unlocking, the barrel and slide need to clear (sounds obvious but some guns do not) before the barrel bottom lug bits the frame and stops. The contact must be on the heavy part of the bottom lug and not on the "feet" or you may find that they break off at some point. The two piece feed ramp needs a very well defined relation ship and it leaves very little room for adjustment which becomes even less if your pistol has much above minimum headspace.
Something so simple as a replacement Mainspring housing may significantly affect your trigger pull and grip safety. Then again, it may not.
I have had two that did and one that did not. These were all replacing a stock plastic part with a steel part.
The tuning of the extractor and ejector is another potential fun event if you don't like spent cases coming back and hitting you in the face.
- Ivan.