Well, I've certainly learned the value of turrets! In this game, one of the enemy AIs seems to be a sneaky type; it's using lots of cloaked ships -- Raiders, Raptors, Planes, Decoy thingies, all sorts of cloak and dagger. So I invested in Laser Turret 1 & 2, and am I glad I did! These turrets mow 'em down. I even used Laser Turret 2's in my most recent system conquest. I made a bridgehead with a mobile builder underneath a forcefield, supported by an engineer for repairs, and I constructed about 25 laser turrets while my fighters/bombers held off the opposition, and used that as a base to conquer the system. The sweetest part was when I killed the enemy command station. As always, the enemy guards immediately made a beeline for my wormhole -- but it was still guarded by a forcefield and those 25 turrets. I cackled with glee as the enemy bounced harmlessly off the forcefield and my turrets methodically took them down -- 250 or so of them. Not a one made it through the wormhole.
Conquest of that system was also entertaining. I was busy congratulating myself on clearing the system, which had an Advanced Lab in it. But I neglected to check the ship list for enemy cloaked ships. So I proudly unveiled my shiny new colony ship and started building my station -- and then 50 raiders de-cloaked on top of it and blasted it to smithereens, lol! (Gotta love this AI!) On my next try, I escorted the colony ship with a Decloaker and some fighters, and I put my new Lab under the forcefield for good measure. The kicker was my unlocked ship: anti-armor, in a game against cloakers! Actually, I'm sure it will come in handy -- I think the other AI may be using starships.
Anyway, now I have a large attack fleet and one smaller rearguard fleet protecting the other "end" of my empire, but the turrets are doing the lion's share of the work everywhere.
I'm also fascinated that the AI's choice of toys can make for such a different game from one to the next. It's like the card game Dominion, as you said earlier. I imagine the expansion multiplies the possibilities by a lot.