Far as action strength....
Both OM and NM Ruger SA's have much wider sears/hammer notches than the various SAA's....except for the OM "safety conversion" guns, which by design, nessesitated those areas to be thinner.
The cylinder latch (AKA bolt) on the ruger is thinner than on a SAA, but due to it's design, the Ruger latch is way-less prone to failure. In fact, I've seen Ruger latches wear out, but never seen one fail.
Springs?....not so much difference there.
A well made leaf-spring will wear about as long as any other part in the guts. The key words here being "well made". Some of them aint so well made... but I've yet to break a Wolff, or S&W leaf-spring in any revolver that I own.
If leafs bothers ya though, you can also note that;
Uberti long-ago began using a coil hand spring, which is captured in the frame via small retainer screw...a feature that Ruger would have done well to utilize but did not.
There are piano-wire type bolt/tigger springs available these days for virtualy any SAA that you care to name. And coil hammer-spring conversions for some of them.
Transfer bar ingition VS a hammer mounted firing pin VS the OM Ruger system?....to me, that is a toss up. The SAA design is certainly simpler, but either of the three can break something. I guess it depends on how many rounds you want to safely carry in your gun...and if you're prone to dry-firing a 6-gun a lot, which is something that an SAA will not tolerate nearly as well as will any of the Ruger SA's.
Then there's long-term maintenance to consider. Meaning that if you shoot these things a lot, at some point you'll need spare parts to be avialable, and affordable. High-dollar guns are made up from high dollar parts. And some gun makers don't furnish OEM parts to us mere mortals.
That, and some "clones" are terrably hard to find parts for.
Some guns are easier to tinker-on (or repair) than others.
A case in point is if/when it's time to address end-shake issues. Doing a proper repair on a Ruger requires a perty-high skill level, AND access to some fairly expensive equipment. On the the other hand, it's real simple to pull the cylinder bushing out of an SAA, add a shim and reinstall it....presto.... the end-shake problem is gone.
On the other hand, I don't know of an easier 6-gun to disassemble and get back together than an OM Ruger, nor of one that needs less hand-fitting than a NM Ruger. Most any repair on either of those are well within the skill level of most folks....even me. That aint to say that "fixing" an SAA is hard, but that design does require a bit more hand-fitting than Rugers normaly do.
That's all I know about that.
DGW