There is a lot of controversey on this topic. Sand definitely causes much less of a risk for adult beardies, but the risk is still there.
I have never used sand, but from what I have read, it harbors bacteria and is very difficult to clean.
Personally, I use tiles, and I love them. VERY easy to clean. Take the tile out, scrub it off, and put it back.
They also hold heat well, wear down beardie nails, and look really nice too.