Berlin: Advantage is that you can fit a lot more live rock down there that can eventually host anaerobic bacteria which will break down some of your nitrates. It is also a host to many copepods and worms and the like that are beneficial to both your clean up crew and as a source of live food for you fish.
Wet/dry: The main advantage here is that because the bioballs are not fully submerged but have a steady stream of water over them this provided a very oxygen rich environment for the aerobic bacteria to convert ammonia and nitrite much fast. This is helpful in tanks that are heavily feed or have very messy eaters which require a large amount of nutrients to be proccesed quickly.
Disadvantage of both is that your going to have to clean those sponges/filter socks almost weekly. Large particles and left over food will build up on those in a hurry and if you don't clean them it continues to break down and can potentially degrade your water quality quickly.
I would say that your best option (as long as you done mind some simple DIY) would be to buy a glass tank and make your own sump. Go to melevsreef.com and he has a whole section on fuge/sump set ups. I would make a sump that has a section for a refugum which are very benificial. He has advantage/disadvange and plans and DIY instructions for all of it. Great site.