It really depends on what you're cooking. Many recipes will require a certain type of cookware. Cast iron is perfect for when a recipe calls for a "heavy-bottomed pan," such as http://how2heroes.com/videos/entrees/chicken-rice. Copper heats up very well in a uniform manner, so it's great for very precise heating. It's also very durable. The only downside to copper is that is can be rather expensive and can tarnish, so it needs to be polished. Again, many recipes now list the best type of pot or pan for the job and that does help in choosing your cookware.