There are 2 complaints about S&W designs repeated ad nauseum that set my teeth on edge:
1. "revolver turn lines are bad and should be eliminated". Fact: causes no harm and shows the revolver is timed properly for rapid fire.
2. "polymer guide rods are horrible and cause malfunctions": Fact: stock captive recoil spring assemblies in the SW/SD series are MORE reliable than non-captive aftermarket steel rod and piano-wire springs.
The Galloway captive steel rod and flat-wound spring assemblies are excellent products, but cost over 3 times as much as the stock assemblies. They do not last 3 times as long as stock, and failures of the stock assembly are rare, most stock units being changed based on perception, not function. In using Sigmas as loaners and trainers since they first came out, I have had NO recoil spring failures. I have changed them after many years "just because" and noticed a small chip out of one rod during cleaning after many years of use: it still functioned perfectly, but I replaced it anyway.
I keep spare recoil and trigger springs on hand as a precaution, and inspect springs as part of routine cleaning. The trigger spring is a higher failure rate item than the recoil spring.