Wool might be warmer, but it is more demanding. Wool does not like to be washed in warm or hot water. Wool should always be washed in cold water. And wool garments should never be put in the dryer, unless there are special instructions.
Some of the ankle warmers/boot toppers are knit from wool yarn. I'm trying to figure out an easy way to mark the ankle warmers/boot toppers that are made of wool.