Look at the Kelvin Temp.
Lower Kelvin temps = more light.
Higher Kelvin temps = more white color.
So - the Extreme White is a 4000 K bulb.
The Platinum Super White is a 3800 K bulb.
In theory, the Platinum Super White would be slightly brighter at the same wattage.
At the bottom of this web page, you'll see a chart comparing true Xenon HID assemblies with different colors. At 4200K, the light given off is the brightest in lumens. At 10000K, the light given off is 1/2 of the 4200K bulb.
http://24.248.84.138/hummers/headlig...visionplus.htm
The same principles apply to Halogen/Xenon filament bulbs.
HTH,
Steve