dmc888 - I believe the idea behind a BB is that there is no waste material to build up and get trapped in your sand bed. As it was explained to me, a lot of LR will be the only biological filtration needed and your mechanical filtration is your floss/mesh sock to remove solids and your skimmer. You also need good circulation in your tank to kick up any solid waste material and allow it to drain to your sump or whatever you use for mechancial filtration.
It makes sense, but I think it comes down to asthetics, do you prefer the look of sand or glass/coraline build on the bottom.
I'm trying to decide which way to go on my new tank, I have a 4" dsb right now but a bb is truely maintenance free.