CB - Reef sand is calcium carbonate based, and anything that is calcium carbonate based is normally good for a reef tank. Like Southdown Playsand. It means that it is most likely free from unwanted metals and other compounds that we would not like in our aquariums.
Livesand is filled with bacteria, but not necessarily with critters like pods and worms that are neecessary for a healthy sand bed to help keep it turned over.
Live sand from another tank would have the best of all worlds, bacteria, pods, and worms.
Thomas