Copper wire can handle a 20-40% higher electrical load for the same gauge of wire.

What other differences are there between copper and aluminum wire?
The main differences between copper and aluminum wires is the resistance of the material. Aluminum and copper are both commonly used conductors, but copper not only has a higher conductivity than aluminum, it is more adaptable, with relatively high tensile strength, and it can also be soldered. For all boat and RV applications, copper is highly recommended over aluminum.