They are not brighter and they do not improve FE......if they are brighter, they are illegal and will get your car impounded by the LEO who is having a bad day.................
That is not true at all. You can most certainly can buy lighting upgrades that put more light on the road, consume less electricity and are legal. They aren't going to be cheap and you will never see an economy improvement due to the lower electrical consumption.
One of the worst thing folks do is to put HID or LED bulbs in housings designed for incandescent bulbs. They are certainly brighter but the bulb is not positioned in relation to the reflector correctly and will create a poorly focused beam with a lot of glare. Those will definitely attract the long are of the law.