for those wondering, those scratches are where the non-stick coating has been scraped off (usually by metal utensils or cleaning utilities like steel wool), which means that food will stick more in those spots. plus, there runs the risk of more bits of that coating coming off into your food as you cook.

Non-stick pans and skillets are best for medium heat as they don't conduct heat as well, and for wetter foods like eggs and fish and pancakes.

On the other hand, cast iron pans and skillets don't have a built in protective coating. The metal will absorb grease and fats as they cook, building up an equally efficient non-stick coating of its own. And without the chemical coating that non-stick pans come with, there's no risk of any of it flaking off or melting into your food. They can handle higher temperatures without damage, and they get hot faster on the burner. Beef, pork, and chicken are best cooked on cast iron.

You don't want to let them soak in soap because it will remove that grease coating that makes the cast iron pan's non-stickiness, plus absorb soap that might melt back off into your food. A soap and sponge rub down is all it needs.