After much experimentation on my Easy Racer bikes (Tour Easy then Gold Rush), I have ended up with a
SON generator hub and a
Lumotec IQ Cyo headlight on a
Terracycle mount. This is the Cadillac of lighting systems, but it truly lights up the road and it will never need to be recharged and doesn't slow you down.
No matter what you choose, you want the headlight to be in front of the fairing. Mounting it behind the fairing will create reflections and backscatter that will ruin your night vision.