Well 240hz do have some benefits, most people will be happy with a 120hz tv. Also the hz of a tv is not the same as the motion of the tv. Hz cannot be turned off only the auto motion can be adjusted to on,off or customized.
120hz has about 50% better picture than a 60hz where a 240hz tv is only about 20% than a 120hz. Most i doubt will notice a difference between a 120hz or 240hz tv. It's really all about the content, normal tv watching you wont see a difference. 3D, sports and action movies will get the most benefits.