intake charge more, BUT, I remember asking the same question to my buddy who uses these systems alot and he said that the colder the fluid, the farther it should be form the intake ports of the manifold, because if it's really cold, the water may not vaporize fully before it enters the cylinder resulting in misfire and stuttering. He uses a dual setup on his supra drag car and has a cold bottle for the jet before the IC, and a hot bottle(hot water) for the jets in the manifold.
