Here goes again, with apologies to those of you who have already bought one.
I've worked with metals for most of my 62 years, have owned a machine shop for 30 and have a lot of experience with almost every engineering material in common use anywhere. I know what I'm talking about when it comes to metals.
Many or all of the 1911 lookalikes now made have varying amounts of Zamak or some other zinc based alloy in them. Zamak (Any zinc alloy) is at the very bottom of the engineering materials group, in fact I can't imagine anyone other than a dishonest entrepreneur who would choose any zinc alloy as the main material of a gun with his name on it.
Colt's Ace, as far as I know they are made of good materials.
Kimber's conversion, the slide is aluminum, not my choice for best but a gazillion times better than zinc. (GSG's slide is supposedly aluminum but the frame is zinc)
As for the rest, I don't know.
But also, to say that any of them is a 1911 is a stretch, none of them locks up like a 1911, the Kimber and Colt are 1911 from the slide down, so the trigger and sear are the same, that's what you want right? Llama made a true 2/3 1911 in .22, all steel, if you can find one. But for the full sized 1911
I'd probably go for the Colt, as the slide is, I believe, steel, and though the admission price is high the value can only go up.
I just wish high quality gunmaking wasn't a dying art, and I wish the American gun buyers knew more about materials.