When considering the choice between metal and plastic for air conditioning, metal is generally considered the better option. This is primarily due to metal's superior thermal conductivity and durability compared to plastic.

Metal, especially aluminum and copper, is an excellent conductor of heat. This property is crucial in air conditioning systems, as it allows for more efficient heat transfer from the refrigerant to the condenser coils. According to a study by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), metal coils can transfer heat up to 30% more effectively than plastic coils. This efficiency translates to better cooling performance and lower energy consumption.

Moreover, metal is more durable than plastic, which is particularly important in the harsh conditions often encountered in air conditioning systems. Metal is less prone to cracking, warping, or degradation over time, leading to a longer lifespan for the air conditioning unit. The U.S. Department of Energy reports that metal coils can last up to 20 years, whereas plastic coils may need to be replaced more frequently, leading to higher maintenance costs.

Additionally, metal is easier to repair and maintain. In the event of a leak or other issue, metal components can often be replaced or repaired without significant disruption to the system. Plastic, on the other hand, may require more extensive repairs or even replacement of the entire unit.

In conclusion, metal is the superior choice for air conditioning due to its superior thermal conductivity, durability, and ease of maintenance. These factors contribute to better overall performance and lower long-term costs compared to plastic.