stainless wear rings will last better than plastic if your in water with a lot of debris in it like small sticks/twigs but if your having issues because your sucking up small stones/shells the plastic ones are better to have in my opinion because they are more forgiving on the impeller, if you have a stone jammed in the pump with a stainless wear ring it can bend the impeller easier where a plastic wear ring may give more and not damage the impeller.
IDoSeaDoo I noticed that you did a engine swap project with a 03 gtx s/c do you still have a plastic pump on that? if so check your wear ring, those plastic pumps used to warp over time, once the pump warps then it wears the wear ring in two spots typically because the impeller is tilted in the pump, the stator in the pump flexes in the pump under heavy loads and eventually stays in that position, people replace the wear ring and it may work well for a short time and then it starts to cavitate again, the only way to fix it is to replace it with a cast aluminum pump