Personally I would not hesitate to buy a new Ruger or Smith & Wesson if they made something today that I wanted (and haven't hesitated). However, I feel like this is sort of an internet meme at this point, from a steak-themed ad campaign S&W had years ago. A Ruger GP100 in .357 in any given barrel length is for all intents exactly the same size and weight as an L-framed S&W (686 or 586). There is nothing heavy or large about it. They no longer make the Security Six, which was slightly heavier and larger than a K-frame. However, Ruger also never expressed concern over that firearm's ability to handle magnum loads (more in a bit on that).
The Super Redhawk is a significantly smaller and lighter gun than an X-frame S&W. Both are able to contain the incredible 65,000 PSI MAP of the .454 Casull, though the S&W is of course big enough to also chamber the much longer .460 Magnum that has the same MAP specification. But Ruger puts 6 holes in their cylinder vs just 5. They are not exactly apples to apples as the S&W is in the longer .460 and the longer and larger .500, but I do think it illustrates that Ruger can make a very strong and relatively light product in spite of the generalizations about casting vs forging.
S&W specifically (and successfully) petitioned SAAMI to lower the MAP of both the .357 and the .44 Magnum out of concern for their K and N-frame revolvers. So one could reverse your generalization about Rugers being heavy for caliber and instead suggest S&W's are weak for caliber. There's also more anecdotal evidence, things like blast shields being cut through on aluminum frame guns like the 329, etc. (However, I think it's cool S&W makes guns like that in the first place, and it's not unreasonable to expect they can't handle the same steady use as an all steel gun will.)
As far as the original question by the OP, that last bit would only bother me if I planned to shoot heavy reloaded .44 Mag, or boutique ammo like Buffalo Bore, Underwood, etc. I don't have any concerns with shooting powerful factory loads (like American Eagle) from my N-frame, and haven't thus far come to regret that. I do save the stout 300gr reloads and such for my Super Redhawk, though the S&W may handle them just fine (the internet has me worried).
The .44 Special actually has a longer maximum cartridge length than the .44 Magnum. So the cylinder would definitely be long enough. However, I would imagine if Ruger thought it could handle it, they would have reamed it as a Magnum. The barrel shank is a lot thinner on the GP100 in .44 than in .357. Smith & Wesson solved this on the model 69 by using a two-piece barrel, which allowed for a much thicker barrel shank than would otherwise be possible. However, it is still thinner than an N-frame, for example.bearfacedkiller wrote: ↑Mon May 07, 2018 7:19 pmThe cylinder is certainly long enough and it is a sturdy gun. I am sure the answer is no and I doubt any gunsmith would do it but if S&W can make a 44 mag L frame I don’t see why Ruger can’t make a 44 mag GP100.
Who knows if Ruger will ever do this or not. 6 months ago people said the same thing about 7-shot cylinders, maybe the Ruger couldn't handle them, etc. Then they released the 7-shot .357 GP100.