Like the 2nd post.. you run up against the limited capacity of Batteries ,
like a bucket full of water with a hole in the bottom.
more watts = a bigger hole.. bucket is limited in size.. so run time shortens.
hub, wont slip in the rain, or bottle dynamo, that will, offers the electricity to be made as you need it .
one watt LED light may not be the Best , but an example the Planet Bike (US brand) imports
a version with a 2 AA battery, and also makes the same light
with a wire to connect it to the front hub dynamo with a plug into the hub ,
and a plug inline , to remove the light, and put it in your pocket when you lock up the bike..
[I, FWIW, just got a Shimano-Brompton Dynamo wheel for $100,
& B&M LED head and taillights to run off it, for another $ 80.
or thereabouts .
still have the battery light clip on the handlebars, that is a tight spot superflash, and a blinkie se , up higher .. on the bike.
so both come in at under the $300 ..