I haven't run a "simulator" but over many games I've come to the conclusion that a defense focus is a cheaper and more efficient use of resources. As part of defense, I include shields, armor, point, passive hull upgrades, and ship components that add hit points. Playing on masochistic, I can usually ward off MUCH superior offensive fleets with minimal weapons and huge, cheap defenses. For this strategy, the Iconians are particularly well-suited with their cheap hull upgrades and "self-healing" ability.
I should add that I always play with tech trading/stealing OFF.
This strategy works particularly well for the good ethical alignment, which gets those powerful added defensive measures, like "telepathic defense" and "subspace rebounder".
A case in point: The mega event, when (Woe to all) the Dread Lords arrive in the universe. Those guys have end-game beam weaponry, and massive damage per ship. They never mount defenses, though, and have very low HP. I've never had much trouble dealing with them with max shield defenses and even mid-level weapons. The AI usually gets creamed by their roving destroyers.
PS
Fleet battles last a very long time with this strat; just hit "done"