50/50 all good IMHO
The plastic ones work fine.
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This is a truth, as plastic guide rods are non-load-bearing parts. And they will not bend, rather, they will flex if something with the return spring occurs. But like any plastic, flex it enough and it will weaken and eventually break.
With that in mind, metal, or stainless steel guide rods will never break via something wrong with a return spring running over them. But one will hear the_argument that because metal won't flex like plastic, one may be inviting a hang-up if such a return spring "event" took place and it bends the rod, the bend is permanent. If such an event took place, I feel that far more damage has occurred to the entire gun to have caused such a force on a bent metal guide rod, be it, from some kind of over pressure event or other major failure of the gun itself.
Either way, IMHO, one's chances are slim with either plastic or metal.
As mentioned, and I agree, one benefit of metal is the additional weight which, for my Beretta Px4 40, replacing the plastic guide rod with a stainless steel guide rod did give the gun more balance, and helped the gun return, a tad better, smoother, with less "feel of recoil" and improved faster, more accurate, back on target shots.
Granted, like waxing ones car, it runs better, faster, than a dirty car, and one's mindset is half the battle, if not more.
But one thing is for sure, they look far better, they will never break or bend IMHO, and with stainless steel vs black plastic, one can see IF, and when, ones guide rods oil and its surface needs cleaning. And, metal will not be weakened by any cleaners used on it, unlike plastic can with some cleaners, oils with cleaners in them (car oils, in general).
Which, I've got to say, having gone thru some 550 rounds, for a total of 1000 flawless rounds thru my new, replaced, Px4, the guide rod has yet to show any dirt on the oiled metal, un-captured guide rod vs the black, captured, plastic guide rod when cleaned with spring remaining on rod when cleaning it as best one could.
With that in mind, shoot your guns with peace of mind whichever guide rod you use/choose/have, as the hopeful_fact remains, they are a non-load-bearing part, under normal or accepted load factors, with replacement return springs, replaced, before such a weakness of a return spring becomes a factor with one too many slams.
Ls