Just another note.
I've used 2 years from now a 4300K 35watt HID set from Xenonkungen. I used it in my other vehicle. The bulbs were H7, so I couldn't use them for my 159. I bought another set for H1, also 4300K, 35watt (Luxpro).
There is a big difference which starter/ballast I use with my new H1 lamps. When I use my old XK ballast, I have nice, white light and when I use my new purchased ballast it stays a little blue, not so nice in my opinion.
Last weekend I retrofitted a E90 BMW with 4300K xenon (just a private label here in Holland), which was so white, I thought it turns out a little yellow: also a set 4300K with 35watt.
Conclusion of the story: It strongly depends on which set you buy, and not only the bulb, but also the starter which color it gets after a while. 4300K is in this market never really benchmarked, I think.
...just my 2 cents