I am no nitrous oxide expert or anything but I've read a fair amount about it and I know the main differences.
If you guys have absoultely no clue what you're talking about, don't post like you do.
The difference is that a wet system only has a single sprayer that will be located right before the throttle body. Before it is sprayed, nitrous oxide and fuel is mixed. An equal mixture of nitrous oxide and fuel is hard to achieve across all 4 cylinders.
Direct port systems have as many nozzles as you have combustion cylinders, in our case, 4 nozzles, 4 cylinders. The 4 nozzles placed on the Intake
manifold which is AFTER the throttle body. Direct ports ensure an equal amount of nitrous oxide and fuel in EACH cylinder since each nozzle will spray the same amount.