bumping this up...still wondering...

The K rating refers to how warm (yellow) or cool (blue) the light color is.

The brightness is the lumens.

For me in the bathroom I like a high lumen (bright) bulb, with a low K rating (warm white).

Stay away from those "daylight" bulbs. I put them in our office, and the quality of the light -- for lack of a better term -- is just weird. The blue tone is "off", unnatural and even uncomfortable in a way that's hard to define. I agree with the terms "bright and cool" from the above list, though I would go with "over-bright and cold". My husband, who generally doesn't notice such things at all, complained and asked me to replace them.

I found not all bulbs labeled "daylight" are actually 5000K.

Learned this when I needed a "cool white/5000K" bulb in the kitchen to make my cabinets look better with my countertop.

The cool white (4100K) -- best!, or even the daylight (5000K) looks great for kitchens, I'd think. But then again, I'm a food blogger and take pictures of my meals, and this would provide greater accuracy. No orange cast to everything. Warmer would be fine and perfect for bathrooms -- I don't take photos there!!