I am going to give you a very short answer to a very involved topic. Ceramic and porcelain are basically similar products. There are very good and very cheap versions or each product. When you go to your supplier, ask about the hardness rating. Softer cheap tile usually has a redish tint on the back side and is made from softer clay, typically in Mexico. Some of the better grades come from Turkey, Italy etc. and have hardness ratings of 5 or above and have a gray or whiteish back. Most ceramic tiles have a thinner glaze finish than Porcelain. I usually prefer a porcelain glaze on a good hard base in shower and bath applications. Rather than hitting the box stores first, go to a few tile specialty tile stores where a good knowledgeable sales person can give you a good education on the differences. If and when you feel comfortable with your knowledge about tile, find a professional flooring liquidator in your area where you may save anywhere from 40 to 80% on overages, returns or closeouts. I recently purchased 600 sq feet of Turkish porcelain grade 5 commercial tiles for 60 cents a square foot that retailed for over $8 a foot, at a local flooring liquidator. (overages from a hotel job) Huge savings.