Wet/dry has many advantages, my favorite being, given proper placement of the tank, you can plumb through the wall into an area that accommodates a larger sump and easier access. My reef tank sump is in the garage behind the tank. I can make all the mess I need! I think the "pros" on the forum will have to give testimony as to how the high flow rates affect CO2 transience though. Seems like it would be harder to keep it exposed with all the water movement.