A1: Most common are austenitic stainless steels, grades 304, 316 and 317. These have the highest corrosion resistance, are non-magnetic and can be hardened only by cold work (annealed 300-series stainless steels are not magnetic, but they may become magnetic after cold working).
A2: Next-most common are the ferritic stainless steels, grades 430 and 434. These are magnetic and can be hardened by cold work. The price is lower than that of 304SS due to the lower amount of Nickel.
A3: Least common are martensitic stainless steels, grades 410 and 420. These alloys have the highest hardness, are magnetic and can be hardened by a combination of cold work and heat treatment. The price is lower than that of 304SS due to the lower amount of Nickel.