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The bluer it is, the more glare to on-coming traffic as well. There's a great, long scientific explanation for this, but suffice it to say that it is easier on other's eyes (especially older people) if you have the lower Kelvin range. It's also easier on your eyes, especially if you're driving distances at night. That blue range of light looks cool, but it's not normal for our eyes to focus in that spectrum so it can cause eye fatigue.
4300-5000k gives you both the most possible output lumens and it's the easiest on the eyes.