It all depends on what you want to do in managing a reef aquarium. Different methods. These days DSB in the DT is old school for many hobbyists. It had (has) it's benefits and overall functions. Some burrowing fish would like the deeper substrate as well. Some require it. But if your not keeping those.. then it's just down to biological functionality in having a DSB. In the older days it was considered a must have. Not so much now. Though in certain applications in can still have benefits.
Personally, I'd do a BB. OR a BB with just a "dusting of sand" to cover sight of the glass if you don't like looking at it.
Depending on how much glass shows- the spread of your rockwork, corals etc..
Overtime besides it's many benefits, people found that eventually deep sand beds built up enough toxins after the first inch or more deep that it made various things difficult. Leaching out in the tank and change outs could become disasters. So, a lot of people turned to an even heavier emphasis on increased Skimming (even though it was done in many situations even with DSb's) combined with a "cleaner", so to speak shallow bed or No sand at all- BB.
Some people have opted to have BB DT's and still keep a "Remote DSB". One that though plumbed into the system, can be cut off from the DT for DSB teardowns- so the DT is not exposed during such occurances.
They are useful for beneficial bacteria, home for various lifeforms especially clean up crews and in a "remote" situation- even a healthier nutrient richer area for growing pods or making it into a refugium to grow Algae or plants. Supplying your system a healthy zone for such things.
But whether you have a Remote DSB or not, I'd go for a BB in the DT or with just a dusting of sand for visually pleasing cover of the glass only.
But that's my opinion. I've had all 3 (DSB, BB and the dusting) I also have had a DSB style refugium on another system in the past that worked really well for me. Lots of pod production from it. Currently, I have a dusting in my DT and NO sand at all in the sump of the current tank. No refugium on this particular system.