Destroyers. C'mon, they can move pretty darn fast, especially if you have the right trait and wonder. They are fast-moving, hard-hitting, and you can make more of them with the same amount of shields as compared to the Battleship or the Cruiser. AEGIS look cooler, and are better vs. airplanes, yes, But I still prefer the Destroyer. I usually build a bunch of Destroyers, maybe a Battleship or 2, some Nuke Subs with Nukes just in case, and some regular Subs for surveillance of AIs.