Hi,
I have a 29 gallon tank that I used to have a 2" cc bed in. I moved about 6 months ago and took the opportunity to change over to a DSB. Trust me, if you saw and smelled what the cc bed was like when I took it out..... there would be NO question to go with a DSB.
This is a no brainer, if you are setting up a tank go with a DSB no question!