I'd rather have the fringe worlds: no flank.
But longer distances between planets to defend. Take a look at the core, now imagine that every planet there has PD and Long Range Sensors. How difficult would it be to find space within PD protected space not covered by sensors? How many PDS are likely to be able to target anyone location? If you want to turtle up area's near the core are the way to go. Of course it takes months to reach it so that is a set back.
