it depends on whats in the tank... most i like a combination of rock, plants and wood. but in my 75 where i have a big pleco and crappy lights, its predominantly large driftwood. in my puffer tank (high brackish) plants wont grow and i really dont like fake plants so its mostly rock work with sand, crushed coral and shells.
I like a mix of everything also. But it has to depend on the fish also. My cory tank has little rockwork to give more room for swimming. The tank pictured is my new ramsetup. I added a piece of driftwood and flame moss on top of the rocks on the left side also.