Hi,
I prefer cool. I guess it's all down to the colour temperature of the LEDs and what you like. Cool ones (higher colour temperature in degrees Kelvin) are more blue - nearer midday sun, warm ones (lower colour temperature) tend to err more towards the yellow / red end of the spectrum (not quite to that of incandescent bulbs and the lower temperatures pushing to candle & carbide light). I prefer the more blue end as that's nearer brighter daylight. I guess it's all personal preference at the end of the day. I suppose almost a Coke vs Pepsi debate! Slightly warmer may look nice in photos - thinking of the old school 81A filters here, but beauty is in the eye of the beholder, and everybody's eyes are different. Some cheaper LEDs seem to have a purple or greenish tinge which isn't that nice so best avoided.
Still going back a good few years can't beat the warm glow of a carbide at the bottom of something cold and continental, yet there again white LEDS weren't invented then, and lights of the day were incandescent which tended towards the lower colour temperatures, i.e the yellow end of the spectrum so that's what your eyes adjusted to after a while, so it seems to me the colour of a cave is what you light it with.