The game has one skill for knowledge of the Core Worlds and one skill for knowledge of the Outer Rim. However the galaxy has many regions - Deep Core, Core Worlds, Colonies, Inner Rim, Expansion Region, Mid Rim, Outer Rim, Wild Space and the Unknown Regions.
I suggest that Deep Core uses K/Core Worlds, but often at a higher difficulty.
The Core Worlds clearly use the K/Core Worlds skill.
The Colonies should use the K/Core Worlds skill.
The Inner Rim uses the K/Outer Rim skill (unless you want to better balance the number of regions that use each skill or you think that the Inner Rim is under strong enough Imperial control that K/Core Worlds makes more sense.)
The Expansion Region uses the K/Outer Rim skill.
The Mid Rim uses the K/Outer Rim skill.
The Outer Rim clearly uses the K/Outer Rim skill.
Wild Space and the Unknown Region uses the K/Outer Rim skill, but often at a higher difficulty. If an area is truly unknown than this may be an Impossible task.
Areas only partially under Imperial control, such as Hutt Space, use the K/Outer Rim skill.
Thoughts?