I would think the best temperature should match daylight. After all, humans see in the visual spectrum of daylight. I think 4800K is closest? The Philips bulbs I purchased measured about 106 Lux at 25 feet.
2013 MP4-12C Spider
2013 Audi S4
2012 MP4-12C coupe (sold)
2008 997 GT2 (sold)
2007 997 TT Ruf RTurbo conversion (sold)
2005 Cayenne Turbo (120K miles now sold)
2002 996 TT Protomotive tuned (sold)