1911's as a whole are a funny bunch. Like women (or men if you're a woman forum member), each has it's own personality and quirks -- good and bad! Some people buy a fully loaded semi-custom 1911 that won't go 20 rounds without a failure and some buy the basic MilSpec that runs and shoot great. You can't anticipate it until you shoot yours and keep track of which ammo gives you problems and which shoot great.
Don't go cheap on the magazines though, they are the heart and soul of the semi auto. What do you have if you have ammo, the gun but a magazine that fails? A single shot pistol, that's what!
I haven't shot the SA MilSpec so I can't comment. I do have several series 80 Colt 1991A1's and have no problems with them at all. They've been great and, to be honest, expected problems from rumors that I've heard. But none have occured. Just personal taste on whether you want series 80 safety or not and there are other topics list on this forum that disuss that so I won't go into pro and con discussion here.
My carry guns are series 80 -- Colt Officers XS, LW enhanced Commander and a Combat Commander 1991A1. Target guns are usually not.
As for customizing, again, that's personal taste. As a matter of fact, my next project will be a SA MilSpec with match barrel, reliability and trigger job. That's it. I want to build a pistol that looks totally like a MilSpec gun but is target grade accurate. But I'm only doing this because I have others with the full treatment of beavertail, great sights, trigger jobs, etc.
You need to let us on the forum know what you want to do with the gun (self defense only, target shooting, carry gun, ect). There are much more informed and knowledgeable people on this forum than I that can probably have much more and detailed input once your useage is determined!
Just my 2 cents of importance: reliability, good sights (like Heinie, MMC or Novaks), trigger job, dehorning and accuracy -- in that order. This is a great forum and there are great gunsmiths and pros that will probably add much to what I've said. I'm an armchair quarterback compared to others on this site!
Good luck and hope I didn't go too long with this post! :smile: