I've done sand, then BB, then sand again, and now I'm dying to go back to starboard....
the sand is great for the organisms who use it/need it...otherwise, get it the hell outta my tank! Pain to keep clean, can't ever get enough flow (its a shallow tank though), always worried about it getting under the magnet and scratching the glass. if you want it for filtration, you're better off with a dsb-in-a-bucket b/c detritus will not be allowed to settle on its surface.
BB is rediculously easy to keep clean...but only if prepared corectly. Cooking your rocks is a must, and you need a lot of alternating flow to keep detritus in suspension. get used to siphoning, at least at first. it'll decrease as time goes on.
of course, your experience may be completely different :wink: just go with whichever one sounds better to your style, and organisms. whichever you choose, do lots of research to learn how to do that option correctly.