Buy the biggest one you can find. They are great for bulk cooking batches of caseroles for the freezer as well as pot roasting chickens and joints. Wherever you buy them, they don't come cheap. Probably the best option is a day trip to France when I gather they're cheaper to buy. There's only one snag with them. As you get older, they become increasingly heavy to lift in and out of the oven when full of boiling hot liquid ! Possible Googling "best prices Le Creuset casserole dishes" might track down the most competitive price. (Oh, and after many years of use, the interiors can stain quite badly with sauces but that doesn't in any way affect the effectiveness of their heat retention abilities).