The two bulbs are not interchangeable. One is designed to be used with 120v service which is common in the US. The other is designed for 220v service as is found in Europe. Plug the 120 into 220 service and watch the bulb go pop. Plug the 220 into 120v service and it will light, but be very dim. I've never tested this, but I'd guess if you compare the output of a 120v, 1000 watt bulb with a 220v, 1000 watt bulb they'd be similar.
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