My tractors have metal fenders while my dads has plastic. There really isnt much difference IMO. They do what they are supposed to, protect the operator from dirt/mud from tires, keep operator station clean(er), and occasionally have a cup holder for your drink of choice. the JohnDeere fenders are definatly not lightly built, in some cases are stronger than the metal ones on my tractors and they dont rust. Metal fenders were on the 4x00 series Deere tractors since my neighbor's 4100 was in a barn fire and it still had the fenders on it. Metal fenders have there up sides but also are prone to dents which is something a plastic fender cant get. Im not sure, to me, they are just fenders. That is my opinion. If you want metal fenders, look at the smaller units in the 4x00 series. I am pretty sure the 4x10 series has plastic fenders since i have driven a rental 4310 and seen 4115's with them too. One new(er) canadate for metal fenders would be the 790/3005, and 990/4005. Or even the 755-955 and the 650-1050.