As it is a regular question I thought I would put up the Which? results (March 2010).
They tested high/low beam H7 form factor bulbs (and HIDs) in a new Astra and measured light intensity (lux), the more the better! Price is per pair.
Factory fit Dipped 91 lux main 48lux
Factory fit HIDs Dipped 164lux 131lux
Osram Nightbreaker +90% £16.49 Dipped 97lux main 63lux Best Buy
Bosch Pure Light £21.98 Dipped 141lux main 55lux Best Buy
Philips Xtreme power +80% £25.69 Dipped 102lux main 62lux
Halfords Super Brilliance +50% £39.98 Dipped 90lux main 62lux
Excellent value from the Osrams and stunning dipped performance from the Bosch.
But just look at the HID performance especially on main beam!