Think about it, wet (or dry I guess but anyone that buys a dry kit is an idiot IMO) kits might not get the correct nitrous/fuel mixture in each cylinder. And correct me if I am wrong, but I think wet kits can puddle up easier in the intake manifold posing the risk for nitrous backfire. I dont know, I wouldnt go any way but direct port.
All this talk about nitrous makes me want to get a smaller turbo and get a 75 shot or something, but that would be more money for the kit, refilling the bottle, more dangerous, and I wouldnt have all the power on tap all the time.