I've learned from knowledgeable gunsmiths: Strength of the revolver is the limit the steel (cylinder and top strap) will withstand before a catastrophic failure. The durability refers to how many rounds (within saami specs) the revolver will take before the lock work and yoke-tube needs maintenance work.

The weak point on a DA revolver is the yoke tube. Excessive endshake is the enemy of a revolver's ability to function. When a round is fired, the cylinder slams back and forth in it's window, which batters the end of the yoke tube. The yoke tube will eventually start to peen and shorten, which causes endshake to increase. This is bad, and if left unchecked, will destroy the revolver.

Ruger revolvers have much thicker yoke tubes, with more surface area on the mating part. They can therefore take many more rounds than S&W revolvers before endshake becomes excessive.

Smith & Wesson revolvers have tighter specifications to work within before they are in need of repair, and they have skinnier yoke tubes. Therefore, compared to Rugers, S&W's need to be repaired more often, given the same round count and pressures.

My personal opinion: I like S&W revolvers for shooting non-magnum rounds. 38 and 44 specials are great, and these guns are very well made. If I want to shoot lots of magnums, it's the Ruger for me. GP100, or the SuperRedhawk.