I've tried both the Philips Diamond vision and Bosch ones.

The diamond vision range is meant to be slightly superior to the blue vision (?) and has a very noticeable blue hue/tinge to it (colour 5k).
Unfortunately, my 1st set didn't last that long (both bulbs blew within a year) and now I'm on my 2nd set. I'm hoping that the 1st set was just a one-off *touch-wood*.

The Bosch, however, remains my favourite. I don't know what 'k' they are, but it was a very noticeable purple and lasted for ages (in excess of 2.5 years). Shame I couldn't find them when I was shopping for new bulbs cos otherwise, I would've gone back to Bosch.

Hope this helps.