ky, i got a question, these systems you are refering to, do they even have a skimmer?? or a refugium, IMO with only lr you should need one of them(but anything is possible)
sand is a much better filter than lr, i have both(and have also used cc and a mix), but i could not imagine 0 nitrates with cc or lr and no skimmer, but then again i could not imagine a clean tank with no filter or skimmer until a year ago
i do admit cc does work fo r some people, and if it is working, why fix it, but in a new set up, i would definintely go with the dsb in stead of cc AGAIN
for jawfish, they are much better off wiht sand, but the dens are more difficult to build wihtout some rock shells and or cc(needs structure), and for diversity, you will get more diverse life with sand then cc in the bed, not to mention the fact that it would take about 20 or 30 icnhes of cc to have the same nnr abilites of sand, not to mention the fact that cc traps dbris, so it does need to be cleaned(some do no t find this a problem, but it is a fact)
and the sand will sift through the sand, the more it is mixed, the faster it will hapen, the sand falls through the cc is how it happens, it jsut takes time, we too had both for a while in our old tank