I found sand easier to clean, if done slowly. Don't rush, no mess! It may cloud tanks (especially smaller tanks) for a short time, in which I recommend using NATURAL sand, none of that died junk. I had two smaller tanks with sand... One with well-rinsed play sand, and the other with blue aquarium sand. Guess which one had a perma-dyed color?
I was not pleased!
Gravel, helps keep plants down. I know some people wh use soil or sand as a substrate will put a small amount of gravel on top. Also helps keep the substrate down too...
Sand is best for any bottom dwelling fish. Cories love it, because first off... If they are frightened they panic and crash into everything! Includes scraping themselves along the gravel which hurts, and can lead to infection.
Others use it for looks... Sand does look more natural than cut rocks. Especially more natural than cut dyed rocks. I prefer anything natural looking. When I move, my 30 becomes a planted tank with nothing artificial in it... From the plants, to the ornaments (using driftwood), etc.