There are four basic differences between a Vision Plus (DOT Approved) and a Hella Euro Conversion.
First is in the lighting pattern. For us in the US the regulations date from the 50's. The US DOT mandates a dispersed pattern that puts a percentage of the light output UP and to both sides of the road so that overhead or roadside signs, which may not have other lighting or reflective characteristics, are lit for you.
The European standard allows all the light to go on the road - they have a law that any overhead or roadside sign has to have it's own, independent lighting or must be highly reflective. So not only is there more light on the road with your low-beams, the high-beams are more precise as well. There is also a triangle of light on the right side to light up roadside signs. Lamps sold in places where they drive on the left side of the road, like England and Japan, have that triangle on the left side.
The effect is that the Euro lights actually put more light on the road for you to drive with, and offend oncoming traffic MUCH LESS because of the sharp cutoff in the lighting pattern. And all of this with the same wattage lamps as in the US.
That's on low beam. Because of the low-beam requirements and the way that screws up the lens and reflector design, it's impossible to get a good high beam. Although the Vision Plus is substantially better than your typical off-the-shelf sealed beam, it's performance falls short of the Hella Euro Conversion.
The second difference is that DOT also required that the lamp have the three Aiming Lugs on the face of the lens. This requirement was dropped in the 2000 DOT Standard when visual aiming was approved. The Vision Plus lamps still have the Aiming Lugs, E-code lamps do not.
Third, the lamp must have DOT molded into the face to confirm that it meets DOT. E-code lamps have E1 molded into the lens.
Fourth, the lamp must not have more than 60 watts on high beam and 55 watts on low beam. The Vision Plus comes with a 60/55w H4/HB2 bulb in it in order to meet the DOT standard. The E-code lamps have no bulb because there are many variations in wattage and color available. It is not recommended to put a higher wattage bulb in a Vision Plus because the light pattern could dazzle oncoming traffic.
