I've been collecting & shooting 1911's for almost 25 years, so here's my opinions:
Colt - the new Colt Government models are really nice basic 1911's. The workmanship is outstanding (as opposed to just a few years ago), they have very good stainless barrels, the sights are plain but nice, the ones I have inspected or own have pretty good triggers and they are accurate. The downsides are plastic MSH, plastic trigger and they often shoot a little high versus point of aim. I put a taller front sight on mine, but that may be an individual issue. The plastic parts function fine, but I replaced them because they just didn't "feel" right. I think this is a great 45 for $500.
Kimber - I own 3 and have handled and shot several others. The Kimber is the nicest finished of the 3 brands, feels the smoothest, has the best out-of-the-box trigger pull, comes with nice sights, and has the usual "full-dress" features such as beavertail grip safety, forward cocking serrations, full-length guide rod, etc. The Kimber will be tighter, more accurate (all of mine do 2" or better at 25 yds) and feel "more expensive" than the other brands you mentioned. I have never experienced any problems with mine except a loose plunger tube which I fixed because I have the staking tool. The downside is I don't really care for the profile of the grip safety (individual matter). Probably the best bang for the buck if slickness and features are important to you - however it doesn't say "Colt's Government Model" on the slide:-)
Springfield - I own one (which I have totally rebuilt) and know of several others. The SA frames are forged, but the frontstrap profile and dust cover profile are NOT per 1911 specs. They are larger, and the gun feels quite a bit different in the hand than a Colt, Kimber, Wilson, etc. They have inferior barrels (2 piece), a heavy and occasionaly gritty trigger pull compared to the others and the barrel fit is poor (not as accurate - mine would only do 4-5" before I fit a Kart NM barrel). The internal parts are often out of spec per the ordnance drawings, and I had to replace the sear & hammer to obtain the correct geometry so I could get the trigger pull down to 3.5# They also use Titanium firing pins with garage door springs to overcome the reduce firing pin inertia. I replaced all of that too. I know of several other SA's that exhibited reliability problems out of the box. YMMV
Bear in mind that Vickers and other custom smiths completely rebuild a gun, and often will even recontour the frame on a SA to feel like a "real" 1911. The SA Loaded you buy bears little relationship to a Vickers, HRT pistol or match race gun other than the name and the basic frame & slide forgings.
If you don't have to have all of the bells & whistles, I would get a Colt.