you cannot discriminate refugiums saying them "not good"
many people have spent long hours researchign on the dynamics of the fuge and many people have benefitted from it.
but it all depends on you to keep the fuge successful
if you think that you can just dump in some sand and throw in some algae and expect it to work wonders, then you are wrong
IMO a fuge is just like another tank and you will have to take good care of it like you do on your main tank
some stuff like iron supplementation can be achieved on accurate dosing and frequent pruning and 24hr lighting can prevent the macroalgae from going asexual and releasing toxins to your tank
as for DSB, you will have to read it up yourself as there are many different ways to set it up
here's a link to start http://www.rshimek.com/reef/sediment.htm
so in conclusion, its up to your own preference to choose whether or not to set up a fuge