Power (Watts) isn't a measure of light output.
There's a few for light, the common one is Lumens and some manufacturer's include this data for true comparison but even then, it gets a bit more complicated as the colour of the light also needs to be taken in to account as the human eye responds differently to different light colours, which is expressed as colour temperature.
I gotta say, it does annoy me the way some of the Snakeoil Salesmen adverse their wares.
A friend of mine dropped around one evening to show me his (very expensive) LED Headlights he'd just fitted in his Moke. We waited until it was well dark outside then we went down the road in each of out Mokes to get a comparison between his lights and mine (H4's fitted with 100 / 160 Watt lamps). He put his on and to me they seems OK for suburban driving, then he went to Hi Beam and again, they were OK but it was clear from the light pattern they'd dazzle on coming drivers. He left his on, then I flick mine on, they pretty put 'blotted' out his except to the right, then I flicked mine to High Beam,,,,,,,,,
One other thing my friend found was that being such a white light they were horrible in heavy rain and fog.
