Well the DSA steel ones are built off Austrian Steyr StG58 parts kits. The SA58 ones are built with commercial aluminum lowers. The SA58s have always been more expensive. I think the aluminum lower drops weight by 1/2 or 1 lb, I can't recall. I have always heard that the aluminum lower is a good upgrade for an StG, but I kind of like the steel just for the sake of knowing it is as close to mil-spec as possible minus import compliance parts. I think of it like a GI vs commercial Springfield M1A but that probably isn't a proper analogy. I think Larry Vickers was really fond of the SA58 for a long time until AR10s started getting better and thinks like SCAR 17s started coming out, so can't imagine anything is wrong with the aluminum. DSA used to make fantastic guns, not sure if they still do though as the surplus parts markets have been drying up.