[Q]

Interesting points of view.
Due to my time limitation I play against AI and I always thought to destroy planets or entire systems is not a useful strategy against the AI. Because in the time and with the resources that are needed to build these stellar manipulation ships I could build troop transports, troops and conventional attack ships and conquer these systems and planets, which allows me to expand much faster. But I always supposed the stellar manipulation might be very valuable against human players!
However you have one important advantage pointed out: the buffer system. If a system is completely destroyed it can't be colonized of course. This will prevent the AI to claim the next system - which is yours - and therefore he will not attack this system.