There's advantages to both a Zerg and a Veterancy strategy. It will depend on the incentives for leveling up.
End of UnleashedElf's quote
By the late game in GC2, you should be fielding thousands of supremely well-spec'd ships in fleets of a dozen or more. You have too, because the AI is doing the same, and you will sustain massive casualties no matter what you do. Ships need to be rolling off the assembly line every week at every shipyard planet, and they need to be outfitted with doom rays and invulnerability shields out the wazoo.
"Zerg" and "Quality>Quantity" strategies aren't mutually exclusive; my personal favorite ship is a medium hull I call the "Paragon Soul", with in excess of 400 defense, 75 attack, 15 PC sensors, 20-something speed and maximum life support. It is by any standard absolutely top of the line in every respect. Despite that, I can lose dozens, sometimes hundreds of them a turn because of the way defenses and weapons work, and they need to be replaced constantly or my front lines fall apart within a few turns.
If Galactic Civilizations 3 doesn't radically change the combat system and the way weapons/defenses and 'dice rolls' work, then you can expect that trend to continue, and once more even the mightiest ships will have to be made expendable.