From everything I've read, I'm kind of leaning toward the DSB. I was reading some interesting stuff about growing sea grass. A minimum depth for the sand base would be 4" for some, 6" for others. This one article mentions the top 2" should be aragonite, silica, or calcite sand (forgot to note granual size) and the bottom 2-4 inches should be some sort of mud mixed with aragonite or silica sand into a loamy media. I don't know if exact proportions were mentioned. Those aticles stressed not disturbing the top layers of the sand....definitely don't stir it or vacuum it....but to keep it looking spiffy use snails and stir the water over the sand when doing water changes to have your filter take up some of the surface stuff.
http://reefkeeping.com/issues/2006-04/sl/index.phpShe does recommend gobies and such to stir up the topmost layer of sand, but if you are interested in growing grass, get them after the grass is established so they don't plow it up.
That's a link to an article about sea grass that was very good and also had a wealth of info on the sand bed. I'm thinking "mud, that can't look very pretty," but then I think about terrariums I've had....it didn't look so bad. In my mind, I'm setting up at least a portion of my tank to support sea grass, although not really interested in the entirely planted tank that some are doing.
QUOTE (miniwhinny @ Nov 7 2011, 12:26 PM)

BB for me. I've painted the underside sand color so it looks like it has a sand bed but stays spotlessly clean. My long term goal isn't to keep the bottom bare through - I want to cover it in different corals

I love how you have your rocks! Very pretty.