I think, for the sake of visibility, you should go with 4300k. They offer the best output and attract the least amount of unwanted attention from the police. 6000k doesn't have the same lvl of visibility that 4300k offers, but it is a reasonable trade off to have something that looks "blue".
One thing I do find silly about your last post- you are inquiring about aftermarket HIDs, which are illegal, but asking if the high beams are illegal. To answer both questions concisely; they are both illegal. Any vehicle sporting HIDs that are not OEM can be ticketed for violating DOT regulations.
If you do decide to go the HID route- be sure to look up Nitro for a great deal. (Shamelss plug...)