My two cents: the crushed coral traps debris and detritus that causes nitrate to develop making it more difficult to maintain low levels.
While a DSB
does provide you with some nitrate control, if disturbed down the line it can release toxins and crash the tank.
If you do a DSB
it's best to do it in a sump so you can close off the system.
My recommendation is to do a 1-1.5 sand bed of fine aragonite like 1-2mm. That way you have a natural look and it will accommodate fish like gobies that sift sand if you want that. You can add some CC on top for the look if you like.
Face it, we'll eventually get lax in out maintenance and cleaning a CC bed will become the bane o your existence. I setup my system to reduce maintenance and use a shallow sand bed with sand sifters to keep it clean. Works for me, not for all.