Tonight Cop Bait and I went out with his factory headlamp equipped C5 and my Euro (T84) equipped C5 and did some rough comparisons. Here's a large graphic showing the difference between a US high/low system, a Euro system with factory wattage bulbs, and a Euro system with 90/100W H4 bulbs. There is quite a noticeable difference.
I apologize for the size, but this is the smallest reasonable size to still see the difference.
Of particular note is the "hot spot" that the US lamp pattern has - the Euro beam pattern much more effectively spreads the light across the road, including the shoulders both left and right, for better visibility. When properly aimed, they both reach about the same distance out in front, but the Euro lamp permits better overall visibility of the entire road surface including the shoulders, whereas the US lamp concentrates most of its power on the hot spot.
In the high beam shots, you will see Cop Bait in the flesh, holding up a large ~15 foot tall section of abandoned PVC pipe we found where we took the pictures. You will notice that the PVC is most clearly visible with the Euro 100W high beam, but is still very visible even at the top with the factory wattage Euro 60W high beam.
With the US high beam, you can barely see that Cop Bait is out there, and the PVC is all but invisible. Just behind and to the left of Mr. Bait was a construction trailer with a reflector on the rear - in the US high beam the reflector makes no appearance at all, and with the Euro beam you can see it in both pictures, although its much more visible with the 100W bulb than the 60W bulb.
Finally, you will notice that, because the Euro assemblies are properly aimed, the furthest "reach" of the low beam is the same for both wattage bulbs, but is brigher with the higher wattage bulbs. The higher wattage bulbs really shine (pun fully intended) when high-speed or very dark driving conditions permitting the use of high beams conditions are present.
Pictures don't do the difference justice - the high beams are like a spotlight illuminating the entire night.
All testing was done with the foglamps turned off.
Let's hear your feedback! The total cost of the Euro lamp assemblies was $64, the harness used to run them is roughly $90, and the bulbs themselves were around $15 each I think. One of the absolute best upgrades anyone can make to a US C5, even if you just go with the factory wattage bulbs that come with them.
Hope someone finds this helpful.
Brian - Y5116
NCM Business Member
Yellow/Black '00 Coupe
12.6 @ 115 MPH (2.14 60' time)
"Redshift" on http://www.c5forum.com