I think "Taking Territory", "Destroying Enemy Infrastructure", and "Winning the Game" fall under the benefits side of attacking
Attackers also have the advantage of mobility, and being able to choose the time and place of their attack. While the defenders must cover all entrances.
And you can always use defense ships to attack; you just have to bring along some hefty resupply capacity, or capture the defender's facilities intact.
PS: Sorry for dragging the thread off topic.