The Ruger is a bit stronger and more durable than the Smith by reason of its solid frame as opposed to the Smith's sideplate. Not likely to be an issue over the useful life of the gun, but it's there just the same.
While it's never popular nor encouraged to argue with a Site Admin, but in this case, I'll at least go fishing...
Considering that there are no considerable lateral forces exerted on the side walls of a revolver's frame, how is the screw-mounted side plate a detriment to the structural integrity of a revolver, in this case, of the .357 Magnum variety?
In the 80s Ruger and Smith and Wesson had back & forth advertising campaigns, beginning with Ruger's claim that thicker was better. Of course, a big part of the thickness of the Rugers was expressly dictated by the fact that Ruger was using investment cast steel vs. the forgings that form the foundation of S&W revolvers. These arguments bear out today, where thin cast parts, more often than not, lack the strength of forged components of the same exact dimensions. It would seem that when Ruger set out to topple the K-frame, they were coerced by Materials Sciences to use thicker dimensions, whereas S&W was able to respond with a forged answer of smaller stature.
For us to say that the Ruger frame is "solid" when compared to the S&W seems, perhaps, a bit disingenuous. The frames have been milled out to accommodate the insertion movements, in addition to the operational movements, of the components.
From the aspect of user serviceability, or as we say nowadays
Sustainability, they are two different animals. When one opens a S&W revolver, it is what we call a WYSIWYG experience (What You See Is What You Get). When one drops the trigger group out of a Ruger GP100, the anatomy books must be examined, closely referenced, and bookmarked.
Now, please bear in mind I am not an Engineer, nor a Materials Scientist, nor one who is versed in the Thermodynamics of Firearms Metallurgy. Rather, I am a mechanically-inclined, technically-minded graduate with a focus in the Arts who works closely with the aforementioned types in order to propagate sales of robotic machinery worldwide.
Of course, I own both brands for different reasons. If I wanted a .357 wheel gun for a steady diet of Magnums then either the L-frame 686 or the GP100 would be good choices, at least in my eyes.