I was thinking that a deeper bed would hold more poop, and bad stuff, making a shallow bed, or bare bottom easier to maintain. I can totally be wrong,that's just what I thought/assumed. You may very well be right. :)

Sand beds 4 inches or deeper are not cleaned, in fact cleaning them is very bad as it disrupts the bacteria and you get toxins released into your water. With the deep sand beds you get hypoxic and anoxic regions at the bottom that grow bacteria which denitrify and get rid of SO4. Whys Alives does a good job of explaining it here

Here is an experimental study that compares deep and shallow sand beds with either fine or coarse sand. An interesting read to see what meets your needs. Bare in mind that the experiment was only run for a few months, not the years that our tanks run for.
sand bed experiment