Short answer
Type 304 stainless contains nickel, which gives it better resistance to rust, salt and acidic foods; it is the usual choice for sinks, wet areas and food-contact tops. Type 430 has little or no nickel, costs less and is magnetic, but it corrodes more readily. It works well for dry uses such as shelves, undershelves and equipment sides.
Many work tables pair a 304 top with a 430 or galvanized undershelf and legs to balance cost and durability. Read the spec sheet for each part, not only the top.
A magnet gives a rough test: it grips 430 firmly, while 304 is non-magnetic or only faintly magnetic. It is not a lab test, but it tells the two apart in the field.
Any stainless can stain or pit if chlorine sanitizer, salt or acidic food sits on it. Rinse and wipe surfaces dry, and use cleaners the manufacturer approves.
Updated · By Norpex