Whats the cost offset between the items? I'd go with the metal if its not a heck of a lot more, IMHO. Plastic may warp if you have a lot of sun and heat like here in FL. While on the subject, has anyone bought the louvers for the back window yet? I'm inclined to go for the aluminum ones over the ABS, if the AL units don't rattle like some I have seen in the past.