I'll second what pdlamb said.
You need a light with more cut-off at the top, so the light goes on the road, not into the eyes of walkers, or drivers for that matter.
What are perceiving as "more" brightness is just light wasted up in the trees.

The B&M Ixon IQ is probably the best optics out there. Many lights are brighter, but without the bean control.

If, as you say, you are riding in urban areas with ambient light, it's very unlikely you need something brighter than the Ixon.
There are guys who descend pitch black mountain passes at 30mph with that light!

Tons of info, including actual photos of beam patterns, here:
http://www.peterwhitecycles.com/headlights.asp