Sand is nice, but you have to have alot of it or very little. The less you have the less problems with dead spots and things decaying on you. On the other hand, if you have a really thick sand bed, it well help support alot of worms, snails and living things that will help keep the sand clean.
On the other hand, some ppl just decide to have no sand. If the tank is just to grow corals, i would go that way, bc sand can also host things like ich and other parasites. As for me, sand makes it look more like a reef, and to support all the life that a reef needs, i have a thick sand bed.