Is calcium hydroxide or potassium hydroxide more efficient at removing carbon dioxide?
$\ce{KOH}$ (and $\ce{NaOH}$) absorb $\ce{CO2}$ more quickly and completely than $\ce{Ca(OH)2}$, but they are much more dangerous to work with: caustic to skin, deliquescent (forming a highly concentrated solution that can pour out of the apparatus), etc. For that reason, "lime water" is preferred for classroom use to demonstrate the presence of $\ce{CO2}$.