Each of these materials comes with its own set of pros and cons. For example, steel piping may be very durable but is difficult to work with. Different kinds of plastic are also available for purchase, though they can sometimes crack easier than metal piping. Copper piping is probably the most common material used because it is inexpensive, easy to install and has a long lifespan, especially when protected by insulation.
When making your decision on what kind of material you would like to use make sure that you know how much wear and tear the area you may be installing gets on an average day. A garden tap in a place where cars frequently drive over might need a more durable kind of piping in order to survive. That being said it is also worth mentioning that most plastics can be painted, something that steel and copper cannot do.