I have both the Ruger, as well as a Kimber, and several Springfield 1911's. And to be perfectly honest, I don't think this whole cast vs. forged argument matters in the least to 99.9% of the 1911 owners and shooters out there. Especially with today's ammunition and component costs.
It's all a moot point, because most people simply don't shoot enough for it to matter. If you're a pro the likes of Rob Leatham, and put over 100K rounds a year through your weapons, then perhaps you might be able to make a case, one way or another.
But even then, how many here who compete, have seen a 1911, (any 1911), go down due to a cast frame or slide failing? I've never seen one in over 50 years of shooting. And sending tens of thousands of rounds downrange.
Also remember that Ruger provides some of the best investment casting in the world from their Pine Tree Investment Casting facility. They have produced investment cast receivers for all of their rifles and handguns for decades. Including the Ruger #1 Single Shot rifle, which is considered by many to be one of the strongest actions ever produced.
Not to mention the Ruger Mini 14, as well as the Model 77 Bolt Action. So building a cast frame and slide 1911 is child's play for them. And I wouldn't hold my breath waiting for one to break.