I've experienced both. Compared to a conventional bulb, the contribution is undeniable. Even more power, better lighting ... Do not compare with Xenon, this is not the purpose of these lights. Now Philips X-Trem or OSRAM Nightbreaker? Osram is a little better lighting but are very fragile. A small shock on the bulb or some pronounced pothole, they burn out. Clearly, both in H4 or H1 on my other vehicle, I change every two years max. Philips I had tested early last a little longer for a price halved. So for the little difference in lighting and a better price / quality ratio, I return to Philips.