The GP100 is less expensive to produce than the DA-Sixes were. The main advantage of the GP100 is the front lock-up being right at the front of the cylinder, instead of out on the end of the ejector rod, but that is a slight advantage, more theoretical than real. I have heard very little about strength issues with the DA Sixes, and only on the internet, with nobody claiming their own DA Six had problems. S&W K-frames have had issues with full-pressure 125-grain loads, over time, due to a thin area of steel in the forcing cone area, adjacent to the crane. The S&W L-frame was developed to remedy that issue, with full-thickness metal all the way around the forcing cone. The DA Sixes have the deeper frame, and always had the full thickness of metal around the forcing cone. Don't take my work for it; compare the weapons yourself. BTW, I am not bashing S&W K-frames; I like them too! They just need gentler treatment regarding harsh loads. As for the Ruger sixguns, I regularly carry both a Speed Six and GP100, and have several of the latter; both are great sixgun designs. I doubt I will wear out any of mine in my lifetime.