This is the engineer in me thinking about the issues in a little more depth. I had a good look at replacing my halogens that have the intensity of oxygen starved candles with both H7 replacement HIDs and LEDs - I concluded that more than just the bulbs will be required. I thought I would share how I got to this conclusion. You will probably find it boring and/or incomprehensible but hopefully it might help.
LEDs can now easily produce a more intense light and at a specific colour using less power than existing halogen bulbs. There are however design and semi-conductor issues to consider in their application in specific existing scenarios. I fear these bulbs are created to get people to buy them simply because they are LEDs. They are not necessarily better and may in fact be considerably worse.
Fundamentally, LEDs, halogens and HIDs all work using the same electronic phenomena at the quantum physics level. Halogens and other filament bulbs use heat to excite electrons. HIDs use gas discharge and LEDs use semi-conductors. It is the electrons falling energy levels within atoms that cause light to be created. LEDs are far more energy efficient in doing this hence their increasingly wide usage. At that point LEDs seem to be the favourite to use.
Back to my earlier post. The existing reflectors (an projectors if you have them) will be designed around a standard H7 bulb or similar. The filament runs down the centre of the bulb and within very tight tolerances.
The reflector will be designed such that the reflection of light is designed around that very tightly toleranced column from which the light is created.
HID replacement for Halogens and also these LEDs have the same physical issues when used in a reflector designed for halogen use. The light from both gas discharge and LEDs is created at a different physical way and is more distributed in a completely differently pattern even though it might only fe a few millimetres difference. The reflector designed specifically for the mechanics of an H7 type bulb simply cannot gather and reflect the light to the same pattern from this distributed source.
These LEDs are probably worse in that the light creation is all along one plane and not in 360 degrees. Half your reflector cannot be used so the light pattern in your existing reflector will be completely wrong and potentially severely degraded.
The second issue is specifically on high intensity LEDs. They do run quite hot compared to your standard LED (if you have an LED TV it still feels warm). The high intensity LEDs create a considerable amount of heat. However, heat itself causes them to become less efficient - its a simple quantum mechanics issue. You can see the back of the LED has heat dissipation built in. However, in sealed headlights, there is little opportunity to dissipate the heat. Its quite possible that when they have been on a while, they will become too hot and hence less bright. Not something you want when driving long distances on unlit motorways or country lanes.
If, however, you have an enclosure, reflector and projector lens specifically designed for this LED construction, I'm sure they will be close to as good if not better than H7 Halogens. As a direct replacement, I can't see how they can perform anywhere near as well.
I do hope though that someone can prove me wrong though.
