I'm no gunsmith, but based on my observation, I see S&Ws having 2 weak links Rugers don't share:
Smith's use a single yoke screw to hold the cylinder/crane assembly to the frame. Remove the screw, and the cylinder & crane simply slide off the front of the gun. Unfortunately, hard use (e.g. from lots of reloads) can bend the screw, especially newer guns that use a screw/spring-loaded plunger assembly. Bend enough, and the cylinder won't close, or will even fall off the gun.
Also, the front of the cylinder assembly in Smiths are locked at the front end of the ejector rod, relatively far from where the strain is being applied. Also, unlike the Ruger, Smith ejector rods also turn as the cylinder turns. If the ejector rod gets bent a bit, it may have trouble locking up, and/or affect the trigger pull as it binds on its retaining plunger during rotation.
Serious competitive revolvers shooters aside, I suspect that neither of these is ever an issue for most, though.
Rugers have more metal on board than Smiths.
Ruger frames are cast, whereas S&W frames are forged, so it's a bit of apples & oranges. Thicker cast vs thinner forged may come to the line together, but I'm not enough of a metallurgist to say either way. Nonetheless, this debate continues, though I suspect differences in metallurgic strength aren't enough of a real issue for most to worry about.