to put it into more simple terms than Jeremy (excellent post dood!)
Wet.dry's are very efficient at converting ammonia into Nitrate... not a big deal if you have a fish only system, but for a Reef biotope tank, not exactly desirable.
Rock is very efficient as a complete biological filter (in addition to a sandbed, but lets not start that debate here

) and the trickle system really isn't necessary. As Jeremy explained, the end product with a live rock system is Nitrogen gas. The biggest issue with Bioballs and trickle systems is that the trap waste and allow it to decompose in the system greatly increasing the amount of Nitrate as they process the waste. The problem is, they create an excess that is difficult for the anaerobic areas of the tank to keep up with because they trap alot of waste. A much better approach is to not use a trickle system and to use a standard sump with a filter sock at the most to catch large particulate waste that is changed out every day at the minimum. Then use a good quality skimmer to remove whatever remaining organics are in the system. This makes for a tank with less maintenance and a healthier system.