The general sense that I got from Swift Transition, was that its use was pretty much confined to the individual character with the power, essentially allowing them to enter the Nevernever pretty much at will.
There are some pretty important things about Swift Transition though... First amongst them is that it doesn't specifically state that the character can transition back from the Nevernever... Additionally, Swift Transition allows entry into the Nevernever, it doesn't give any information as to what's on the other side. It could be a nice, peaceful garden. Or the home of some rather voracious worms which want to eat the character.
World Walker allows the character to sense and if need be, open Rifts/gateways between the normal world and the Nevernever. This allows for two-way travel (by the character and possibility others) between the two. At the same time, the power also gives the character with it some information or idea of where in the Nevernever they are.
The downside is that many denizens of the Nevernever don't particularly like it when people open up holes to their abode, and since a Rift is two ways, they might decide to come through (or send something at least) to do something about it.