It is mostly determined by the tensile strength of the plastic. Plastic that is stronger and of higher quality can provide outstanding service. It has a number of advantages to metal tubes, including the fact that it is typically lighter, resulting in less hand fatigue while in use. On the other hand, the metal tube is nearly assured to be tough and durable, so it's a safe bet. It's also more resistant to breakage, has a longer lifespan, and is more durable.