I think that it is safe to say that Direct Port applies to all of the above (safest, most efficient, and better) You then know that you do not risk blowing your engine becuase the same amount of n2o is being applied to each cylinder, but you now have an Intake
manifold with holes all up in it. So if you ever get rid of your nitrous system you need a new manifold.
The only direct port I have found is adjustable 50-75-100. I will never use 100 shot. I like the wet kit that is 35-50-75. I'm sure I would use 75 once in awhile, but that is very risky considering the n2o could be sprayed unevenly.
So I guess the line "if you are going to mod, do it right" applies here. If you want to take the risk go for it. Not me.