It could be argued that pure white (4000K) light is superior due to improved color rendition. But in reality, yellowish light (around 3200K) is probably the safest for night driving. Why?
First off, bluish light scatters in fog or poor weather and blue light has a very distracting effect to the human eye. Try to focus on a blue light at night and you'll realize that it's both difficult and uncomfortable. There's a reason why fog lamps on some vehicles is tinted yellow.
Second, any halogen bulb that tries to mimic a "xenon" headlamp has a color filter on the glass. This filter simply removes the yellowish part of the light output, which means fewer actual lumens are making it onto the road. Hence, it's providing an illusion of better visibility while actually providing less.
If you look up bulb specifications you'll find this to be the case. Bulbs with maximum output (most lumens) are unfiltered. These filaments are driven harder than regular bulbs so they produce more light with the same wattage. A byproduct is that they also burn hotter and have a slightly higher color temperature than normal bulbs (3500K). The consequence is a much shorter bulb life.
Tinted bulbs, such as Sylvania Silverstars, drive their filaments very hard to produce legal amounts of light. Their lumen output is the same as a cheap, standard bulb but with ridiculously short operating life (I think a 9005 bulb is rated at 50 hours!). I bet most of the tinted bulbs on eBay or whatever don't even put out the legally minimum amount.