I've had both...
A BB setup requires very diligent maintenance, lots and lots of water flow, and aggressive filtration and water change routine.
Sand offers an additional home for bacteria and microfauna, and usually gives you a litte wiggle room when it comes to maintenance. IMO it looks better too, and provides a more stable base for your live rock.
I had a BB setup for over 3 years, after having a DSB for 5 years. I moved the contents of my reef to a larger tank last fall, and did a SSB.
MikeS