A defenseless Coruscant is like a tumor. I would have to keep fleets watching over it, since I couldn't have enough shields or turrets. I bombard it so it goes over to the Rebs. They'll have achieved an object, and they have to hold it. SO they'll move fleets to coruscant to protect it, and they'll move command chars and diplomatics there. Through espnionage i know who's there adn how many fleets. If the fleet there is big enough I'l gather a couple of fleets and strike at Coruscant. If it's not and I strike and retake coruscant, I'll be in the starting position, because there'll be rebel fleets around and i'll have a fleet destined only to the protection of Coruscant. Without Coruscant I have more flexibility in my fleet deployments. I can stage hit-and-fade attacks over different sectors without fearing of the rebs striking at my capital.