From the perspective of the durability of the best material should be stainless steel. Speaking of stainless steel, let a person think of is first against corrosion, long service life.
Space aluminum is a kind of high strength and corrosion are aluminum products, has many characteristics, such as lightweight and durable, due to the early used in aerospace industry, so called "space aluminum". But space aluminum will make oxide layer at the slightest touch damage, then oxidation to produce something similar to the mould.
Zinc alloy material, its advantage is easy to make it complicated parts, especially pressure casting, as seen on the market more complicated design of lock is made of zinc alloy material. But the strength of the zinc alloy and rust resistance than stainless steel
In conclusion, or stainless steel is good, price moderate, against corrosion, long service life.