From what I understand, the 5000k are pure white - with no blue. And also at 5000k you get the maximum light output - though I can't back that up.
installation is not quite as plug-n-play as advertised - at least in my expedition, there just simply wasnt space given the amount of wire available, so we had to remove the grill and headlights, using screws and ultimately zip-ties, we had to mount the 4 ballasts, 2 on each side, 1 on top of the other, using screws into the sheet metal, the included METAL brackets and a couple zip ties to hold them all together. Then putting everything back together - it took around 3+ hours give or take... Remember, I also did my fog lamps as well, and if you have fog lamps I highly recommend doing them the same color - the look is very nice and factory looking.
So, the kits I bought from a local dealer cost me $55 each, they are the larger ballast - and the ballasts are digital - what that actually translates into - I'm not sure....
The headlights are HID LOW and HALOGEN HIGH... and the HALOGEN HIGH are much dimmer than the HID LOW

The fog lights are HID only, and they needed to be trimmed just a bit in order to fit properly, but it was pretty simple with a hand held grinder (dremmel) I'm sure that varies from chinese manufacture to chinese manufacture
Here's the front of the truck with the headlights out, and grill out - this was to give us enough room to mount the ballasts behind the grill (well, really behind the bumper) under the headlights... We screwed the ballast bracket into the metal.
HID LOW's ON (test)
HALOGEN HIGH'S ON (test)
(the picture's don't do it justice... It need to see them in person to appreciate the color, and brightness)
Here's the finished deal in my driveway