A copper coil is more effective at transporting heat because it has a conductivity that is roughly double that of an aluminum coil. An air conditioner or heat pump uses the refrigeration principle. The transfer of heat from one area where it is undesirable to another where it is not is the classic definition of refrigeration.
Use of heat-moving or heat-transfer-efficient materials is also crucial. The winner in this case is copper. Refrigeration enables the operation of air conditioning systems. The simplicity with which copper coils may be fixed on the spot if they are damaged is another benefit. And finally, damaged aluminum coils are challenging to fix and usually need to be replaced