In regards to scrying vs. traveling through the Aethyrs (along with the difference between evokation and invokation), the magickian whom scrys or calls upon the Aethyrs without having developed his Khu, is limited by his Khu. It is the Khu that must attain mastery of itself in order to travel. The Khabs is under no such constrants; it can permeate all Aethyrs (as that is where its from).
Just as evokation is the arousal of a part of the microcosm within the microcosm, scrying the Aethyrs is the exploration of the macrocosm within the microcosm.
Invokation being the drawing upon the macrocosm into the microcosm; traveling through the Aethyrs is the microcosm exploring the macrocosm.