Fiberglass bathtubs are the way to go, they are not only sturdy and strong, but last a long time and dont chip, stain or perish.
Fibreglass ones generally have a harder surface (gel coat) and are more resistant to scratching.
cast iron, steal, and fiberglass tubs.
Claw foot bathtubs can be made out of porcelain, acrylic or fiberglass. Claw foot bathtubs were popular in the 19th century and are usually accompanied by a shower.
Acrylic bathtubs can be purchased from department stores that sell bathtubs. Another option is to buy them online. For example Lowe's has a selection of acrylic bathtubs, and from website Alibaba one can find acrylic bathtub models with a link to the supplier's website.
They were steel coated with ceramic, now they are fiberglass.
Cast Iron tubs the finish is stronger in most cases then fiberglass BUT there are new acrylic tubs like Americast that are just as strong (and cost the same) as Cast Cast Iron will not shift like the plastic tubs do BUT you do have a lot more heat loss as the mass of the cast iron is hard to keep warm. Acrylic tubs you have to be extra careful what cleaning agents to use as the finish can scratch more easily
As with all things the term "best" is more a matter of opinion than of fact. Bathtubs are made of glazed stamped steel, acrylic, and fiberglass (and even glazed cast iron if you can find an old one). Each has its own properties, and each can last a lifetime or two if not physically damaged by accident, abuse or neglect.
If you have city water (decent city water that is) a fiberglass unit with typical warranties of approx. 6 years, will do you just fine. Acrylic is best for places with well water and have typical warranties of about 10 years. The difference is that acrylic fiberglass is solid throughout, whereas what is known as a fiberglass unit has what is essentially a spray coating of acrylic on the surface. Thus the solid acrylic fiberglass units are "tougher" It is recommended for either unit to use something like car wax (on the walls ONLY, never the floor, unless you use non-slip mats) to protect the unit, at least once a month.
Never Dull works well with some elbow grease.
Metal baths (enamel on steel or cast iron) retain more heat than their acrylic or fiberglass versions
yesANS 2 Dry fibreglass is lighter than acrylic. Formed to a shape, with it's resin, it's nearly 50% heavier than acrylic.
Most modern bathtubs are made of acrylic or fiberglass, but alternatives are available in enamel on steel or cast iron; occasionally, waterproof finished wood. A bathtub is usually placed in a bathroom either as a stand-alone fixture or in conjunction with a shower. The average time to empty a baby bath is 4 seconds.
There are quite a few objects in a household that may be made of fiberglass. One of these objects is the siding on the house itself. Other objects include insulation, electronics, doors, showers, and bathtubs.