The S&W double action is true gunmakers art. The mechanism is complex and highly fitted.
I have broken 2 S&Ws somehow. One a Brand New model 29 with maybe 2 boxes of factory loads through it, another a used model 66 that was a cop trade-in gun. Both broke their hand or ratchet, The cylinder stop would not engage and the cylinder just spun freely. Might want to have a pistolsmith look over your S&W and if it shows mechanism parts wear, have new parts fitted. Compared to a Ruger, S&W are complex with many more parts.
Not too fond of the fixed-sight guns with tiny notch for rear sight. If you expect your sights to be “on” find the load that fills your need, is on target and stick with it. Can enlarge the notch a bit to shift impact, but not really a viable fix.
Not much on the .357mag for defense. Takes a lot of practice to shoot double-action well and a 4″ .357 is not all that powerful. Most velocities are published using 8″ barreled guns. I would handload and use the heaviest silhouette bullets with flatpoint that I could find or maybe go with the RCBS 200gr flatnose bullet mold cast from wheelweights. But maybe you are a guy who can empty the cylinder in 2 seconds and keep all your loads in a 2″ circle at 10yds? With moderate handloads or non-+p .38s it is relatively easy, just compromises the velocity threshold the .357 needs to make its power.
If this is a main defense handgun choice, might be better as trade material on weapon chambered for a 10mm auto or larger handgun ctg. Probably have lots of guns though.. enjoy; but check-out the mechanism under the sideplate!