Now, let’s first talk about stainless steel gates. With the right materials, it is the most durable among all, due to its strong structure and almost rust free, it can stay intact for as long as one live, now stainless steel is known for its hard surface, it is immune to casual hits on its surface, it won’t leave too obvious marks on it. It can be re- polished to look new. Galvanised Metal powder coated gates. Now notice that I mentioned galvanised. There are 2 types of galvanising method. The hot dipped and the cold dipped. The former is a stronger coating method. This is done before the finishing coat is applied to the frame surface. It is an anti rust coat that prevent the metal frames from corroding ultimately, as metal also known as mild steel, it is not as hard as stainless steel. However it can last as many as 30 years without corroding. However, the finishing coat may need maintenance or re work to make it look new. Those who appreciate classical designs can go for metal gates as some designs aren’t available for Aluminum and stainless steel types. It all depends on the owners design preferences. Aluminum gates, Aluminum materials are soft and light weighted in nature due to it’s non-ferrous qualities. However Aluminum is totally rust free. But due to that, it is easily prone to thorough wear and tear after some 5-10years or so. Have to be careful when handling on its surface as it can be dented easily. Like wise, powder coated coatings do have a life span of around 5 years, the color May fade, re coating has to be done to make it look new. So above are my views of these 3 types of gates... correct me if I am wrong.. 😅. Trying to consolidate more information of them. Hopefully the above information can help you..