I've read that fiberglass doors usually have better insulation and are more suited for cold climates. Steel doors can also be energy efficient if they have a quality interior, but they can cool down faster in cold weather. To find out the pros and cons of fiberglass vs steel doors I would recommend you check out . This site provides a good comparison of the two types of doors. I chose the fiberglass door as it seemed more suitable for my climate and durable, but maybe something else will work for you.