"Perhaps we should rule out planets that are dangerously close to their star, systems with stars near the end of their life, worlds that run too close to an asteroid belt, or anything along those lines that would render the world unstable," Wentar suggests to his companions. "The scrolls would not be risked on such worlds."
Hmm... Inside the dangerous radiation limit sounds like an ideal place to hide something you don't want disturbed. (as long as said item(s) can't be damaged by radiation)
I'm assuming that, as with our own world, there exists suits or other personal protective measures in the Star Wars Galaxy to allow people who REALLY want to, to visit such places for a limited time safely?
Could we possibly eliminate based on each of the six planets' distance from Sith and Republic space? Something farther out might make for a better hiding spot than something that neither had control of but could reach without too much difficulty.
Or any spatial anomalies that make it hard to reach any of them? Asteroid fields, etc.