@cleeds
That would be assuming the identical piece of equipment being used at 110V and 240V, whereas the equipment would be built for the particular voltage being used, so both pieces of equipment would be different so they produce the same Wattage output. If an amplifier manufacturer builds a 100Watt amplifier and sells it in the UK and US they fit the appropriate power supply to feed the amp with what it needs to produce 100 Watts. They don't sell it with the same power supply in both countries as 100 Watt in one and 50 Watt in the other.
That would be assuming the identical piece of equipment being used at 110V and 240V, whereas the equipment would be built for the particular voltage being used, so both pieces of equipment would be different so they produce the same Wattage output. If an amplifier manufacturer builds a 100Watt amplifier and sells it in the UK and US they fit the appropriate power supply to feed the amp with what it needs to produce 100 Watts. They don't sell it with the same power supply in both countries as 100 Watt in one and 50 Watt in the other.