Some differences between acrylic and cast iron tubs are that acrylic tubs are made of synthetic materials; they are also light weight, come in many shapes and make good insulators, while cast iron tubs are generally heavier, solid and hold up well to heavy use. Acrylic bathtubs are usually less expensive than cast iron tubs. Cast iron tubs are also available in many colors, and like acrylic tubs, can come in freestanding and drop-in designs.
Acrylic tubs are made primarily of plastic, which makes them relatively light and easy to mold. They are among the most popular varieties of tubs for creating whirlpools and customized bathtubs, according to Bob Vila. Acrylic is lighter than other bathtub materials, which makes it a good choice for second or third floor bathrooms.
Cast iron, on the other hand, is very heavy and should be used in first floor bathrooms. Because of its flexibility and light weight, acrylic is a common material in long tubs and indoor Jacuzzis. Acrylic comes in solid colors, which makes scratches less noticeable, says Bob Villa.
Cast iron is ideal for shorter bathtubs. It is a popular material for old-fashioned clawfoot tubs, which are free-standing. However, cast iron is also found in drop-in bathtubs, which are surrounded by reinforcing materials like stone or concrete. Cast iron tubs retain heat and are soundproof, thanks to their thick builds. These tubs can be finished with other materials such as enamel or porcelain, which adds an attractive outer finish.