"Which 1911 is best?" is right up there with the "9mm vs. .45" debate. I've shot Rock Islands, Springfields, Kimbers, Llamas (both under that name and "Firestorm"), and Colts.
For me, an arched mainspring housing is a must. They point low otherwise. Despite that, I still want a Para LTC
. If I ever pop for one, it will almost definitely get an arched mainspring housing in short order, but I like to shoot a gun stock before I start fiddling with it and changing things.
I like my Parkerized Springfield Mil-Spec, which I've "pimped out" by swapping a few of the parked parts for stainless ones. It has nothing to do with the functionality of the gun, but having the recoil spring plug, barrel bushing, hammer, thumb safety (went to an ambi-safety at the same time), slide release, grip safety, and mainspring housing be stainless on a Parkerized frame and slide just looks cool to me.
The Rock Island pistols are functionally just as good as any other 1911. The fit and finish on them isn't as pretty as it is on a Kimber or a Springfield, but they'll run the same ammo just as good for half the price. The one thing I don't like about the Rock Island pistols is that they come with smooth grip panels, and I prefer some checkering.
My advice when it comes to 1911s is this: If you find one you like, get it. If you can't find one exactly like you want it, be shocked, then find one very close to what you want, get it, and make the adjustments you need to make it right for you.