To make an aluminium cable with the same energy losses as a copper cable, we have to make it fatter. The larger cross sectional area reduces its resistance and brings the energy losses down to the same as a narrower copper cable.
The two cables in the photograph have similar current-carrying capacity. They are each designed to be able to carry up to 500 A without the conductor going above 90 °C; they will have to carry this current when demand is high but should not be used for larger current.
The copper cable (on the right) is thinner than the aluminium one, because copper is a better conductor. Its cross sectional area is 300 mm2 as opposed to 500 mm2 for the aluminium.
There are four groups of wires within the cable and the groups are insulated with cross-linked high-density polyethene (XLPE). The whole cable is reinforced with steel wire armour.