[Derek]

I ran a PIAA superwhite something or other last year. I'm embarrassed to say how much it cost and although the blue/white light is brighter your eyes are less sensitive to that colour so you actually don't see so well - but everyone else gets dazzled! Even worse,it only lasted about 5 months which is about 5,000 miles for me.
Best solution was to fit 2 relays (one for main and one for dip) and a Philips 50% brighter bulb.