The two steel grades are comparable in appearance, chemical makeup and characteristics. Both steels are durable and provide excellent resistance to corrosion and rust. 304 stainless steel is the most versatile and widely used austenitic stainless steel in the world, due to its corrosion resistance. 304 stainless is also cheaper in cost compared to 316, another reason for its popularity and widespread use.
To sum it up, 316 steel is worth the expense if you need superior corrosion resistance and your application contains water. If not, 304 steel will serve your needs just fine.