Back to the original question, what seperates them? 10 yrs ago it was clearer, 20 yrs ago it was a lot clearer, there are so many manufacturers making better than milspec 1911's now it's not funny, and most of them will work as good or better than an issued 1911 in days gone by, with BALL ammo. That is one thing that seperates one from another, most of the modern pistols regardless of who made it, come with what we call a wide mouth on the barrel entrance, something that evolved and no gunsmith disagrees with, it does facilitate different bullet designs and takes nothing away from shooting ball ammo. If you want a defensive pistol and plan to shoot nothing but ball ammo at reduced distance, the world is your oyster, given that modern pistols come with larger than issue sights from 90 yrs ago, except for some retro, true to spec pistols. Reduced range for center of mass is less than 25 yds. So most will fill the criteria. The old issue sights with the miniscule front sight, did not allow for proper sighting, if you had an elevation problem then you better learn to hold over or under, because it was not tall enough to file down, and taller front sights were not available, nor lower rear sights, but you could file down the rear sight a very little bit. pistols that do not shoot to point of aim or close to it are due to barrel bushing fit, barrel lug fit, link fit or really sloppy slide to frame fit, you don't see that too much anymore.
The original design was for 230grn ball ammo, if that works for you fine, but if you want to shoot hp's or Swc's, it will be hit or miss, some do and most don't without polishing the feed ramp, and the entrance to the barrel. Original magazines won't properly feed a lot of SD ammo.
Last go's back to colonel Cooper, 100% reliable with your chosen ammunition ( that leaves a lot of room, if your shooting anything but ball ), next usable sights, that means you can see them easily ( I like to widen the rear notch to at least .125" ) and a clean trigger break in the 4lb range, I like mine lighter, but 4lbs, and clean works.
So some manufacturers include a lot of this, but if you get a 4lb trigger pull that is clean and not gritty, you have done well, if it feeds HP's out of the box, ditto, the sights are not much of a question anymore. You can do better, but as issued is not bad.
So again, what do you want, 100% reliability, SD accuracy, a decent trigger pull, ( 10 lbs won't work ) and a pistol that shoots were you point it. The rest is making the pistol fit you, a safety that comes off decently and you can re engage with no problem, a grip safety that works for you, mag wells or mag well work that allows for faster reloads. A mag release even if it is factory, that does not take 2 hands to release a magazine. A good gripping surface, whether it is skate board tape or checkering.
I hope I have given you all enough questions to answer your selves.
