I did a bunch of research on this question not too long ago. Basically, the answer depends on how much work you're willing to put into it and what your goals are.
A remote deep sand bed ("RDSB") is a great way to manage nutrients and also stimulate maximum microfauna growth. The trick is that you need ultra-super-very-fine-grained sand in order for it to work optimally. Think silt. You also need to activate the sand with some animals. I think a cup of refugium substrate from a few different fuges would work fine, but if you want to go all the way, Indo Pacific Sea Farms and Tampa Bay Saltwater both have products that would help. You actually need to have pretty aggressive flow above the RDSB as well, in order to provide oxygen to the sandbed. I have a Voyager 4 pushing water in a gyre flow pattern in my 45g refugium with RDSB. It requires careful powerhead positioning and securing the powerhead is important.\
A RDSB is also a potential phosphate sink, which means it absorbs phosphates until it's over-run; this takes many years and shouldn't really be an issue for people with a healthy DSB.
A BB refugium is ultra-low maintenance. It's fine for growing chaeto and mangroves. If you do this, don't forget to have a good powerhead in there - you want no detritus settling, just like with a BB tank.
A shallow sand bed ("SSB") is useful for providing a substrate as a habitat for pods and other microfauna. Doesn't give as much as a DSB, but mysids still like it. You'll want to clean/siphon the substrate every few months to remove detritus. This will work with mangroves. If you have chaeto in a SSB fuge, you may have an issue with dead rotting chaeto settling on the bottom. (I haven't found anything that eats this). Again, powerhead is important.
Hope this helps.
