|Voted Best Answer
Although ALL bathtubs, including porcelain, fiberglass, and cultured marble, can be refinished beautifully, we sometimes recommend to our customers that they replace the tub if it is leaking, but only IF the bathroom is going to be gutted (because sometimes the leak can be repaired). Otherwise, you're dealing with the cost of tearing out tile and plumbing needlessly.
If you are going to replace, definitely go with a porcelain tub. Cast iron is heavier but more durable and more expensive, but will last longer. Steel is lighter and cheaper, but not as durable.
You won't have the discoloration and spider cracking problems with porcelain tubs like you will with fiberglass and cultured marble.