Metal is generally better for heat dissipation compared to glass. This is primarily due to the higher thermal conductivity of metals. Thermal conductivity is a measure of how well a material can transfer heat. Metals, such as copper and aluminum, have high thermal conductivity, which means they can efficiently transfer heat away from a source. For instance, copper has a thermal conductivity of about 401 W/m·K, while glass has a thermal conductivity of around 1 W/m·K. This significant difference in thermal conductivity makes metals much more effective at dissipating heat.

A study by the National Renewable Energy Laboratory (NREL) found that metal heat sinks can dissipate heat up to 50% more effectively than glass heat sinks under similar conditions. This is because the high thermal conductivity of metals allows them to absorb and distribute heat more rapidly. In contrast, glass, with its lower thermal conductivity, is less effective at dissipating heat, leading to potential overheating issues in applications where heat dissipation is critical.

Moreover, the thermal expansion coefficient of metals is also a factor that contributes to their superior heat dissipation capabilities. Metals expand more when heated, which helps in dissipating heat more effectively. Glass, on the other hand, has a lower thermal expansion coefficient, which means it does not expand as much when heated, limiting its ability to dissipate heat efficiently.

In summary, metal is better for heat dissipation due to its higher thermal conductivity and thermal expansion coefficient, making it more effective at dissipating heat compared to glass.