User blog comment:JordanaBrewsterFAN/The Citadel: Destroyed or not?/@comment-24174486-20121220190908/@comment-1679409-20121225044004

Less and/or a less destructive form of energy.

Plus, in the destroy ending, Shepard actually blows something up on the Citadel/Crucible (don't remember which one that part's on) while he/she jumps into a massive energy beam in synthesis, which no doubt has a destabilizing effect.