It all depends on what you want to do with the tank really. For having a larger sized tank my recommendation would be to have both a sump and a fuge. Or, depending on space you could even have a sump/fuge all in one unit.
In most cases the sump is going to be used to hide your heaters and other various equipment. I myself have put extra LR in mine to have an additional place where copepods can live without being eaten by the fish. You can also run carbon in the sump with a filter sock.
A refugium will do several things for your tank. It will help keep nitrates down. Be a place where pods can grow. In basic terms it will be a smaller sized tank where you grow macro algae. There are options to have LS in the bottom or not. In my fuge I just have LR, caulerpa, a light, and my return pump to the tank. I think most people use cheato in their fuge.