Ill post because I build alot of stands made of either material. I build wood stands and canopies for most tanks up too 300 gallons, I build some stands out of metal under 300 gallons where space is an issue, canopies are the same deal, I like metal canopies as they are light weight and strong. All tanks over 300 gallons I build steel stands and steel or aluminum canopies, both metals get powder coated and the finish really lasts forever, your wood even if treated will rot long before a well built and well powdercoated steel structure will even begin to rust...