Steel doors are inexpensive and low maintenance, while fiberglass is lighter weight, durable and can mimic the look of real wood. On the downside, steel doors dent easily and may not stand up to the elements well, while fiberglass is more expensive and can crack visibly under impacts.
There are three types of materials used for most entryway doors: wood, steel and fiberglass. Most people are familiar with the characteristics of wood, but they may not be as aware of the latter options.
A fiberglass door is made with a hard fiberglass exterior and foam core insulation. These doors are surprisingly lightweight, and available in a wide range of styles, colors and textures. Fiberglass can even mimic the look of real wood. These doors provide plenty of insulation, and resist the elements very well. However, they are much more expensive compared to the other materials. Fiberglass is strong, but it may also crack under repeated impacts or blows.
About half the market for entry doors features steel doors, as stated by Consumer Reports. This material is common and inexpensive. The added weight and heft of steel gives it the feeling of strength and a solid look. Steel is low maintenance, but can pick up bumps or dings over the years. This material is not a good choice for areas with lots of wet, cold weather, which can wear away the paint on the door and cause rusting.