Any faction can spam carriers - considering all the light carriers use up 8 supply no matter what and that every faction gets access to a capital ship carrier for 50 supply, there's really not a CLEARLY superior faction for lots of carriers.For what it's worth, though, I'd recommend Advent for the early game and Vasari for late-game carrier actions. Advent get access to earlier carriers and large swarms of fighters/bombers. They all do less damage individually than other fighter options for the other factions, though, and will eventually be eclipsed in usefulness by Vasari strike craft. The reasons being that while Vasari fighters are not as numerous as Advent strike craft, Vasari get access to lots of armor upgrades, while the Advent do not (and fighters/bombers don't have shields). Furthermore, it's harder to knock out the individually tougher Vasari fighters en-masse like it is with Advent fighters. The Vasari carrier also has the microphasing aura that affects all friendly fighters, which can make a huge difference for keeping your fighter craft alive.
I agree with Snipafist. Early game, the Advent can win with their numerical advantage. But later on, Vasari technology beats them. I'll prefer to let the numbers speak here:
Fighters with Full Upgrades:
AdventHull: 50
Armor: 4
Repair Rate: 0.18
Damage Per Volley: 20 Laser
Cool-Down Time: 12
Range: 2400
Speed: 2700
Build Time: 16
Squadron Size: 9(11 in Hangars)
VasariHull: 105.4
Armor: 7.5
Repair Rate: 0.51
Damage Per Volley: 36.9 Phase Missile w. 25% chance to bypass enemy shields
Cool-Down Time: 12
Range: 2400
Speed: 2916
Build Time: 24
Squadron Size: 4
As you can see, 1-on-1, a Vasari Fighter Squadron will destroy an Advent Fighter Squadron since you can't focus fire on individual fighters(AFAIK), and the awesome armory and native repair capability of Vasari Fighters will effectively negate Advent attacks. They'll kill off all 9 drones at the loss of 1 fighter. While the Advent will take 144 seconds to replace their losses, the Vasari will only take 24 seconds. That's 2 minutes worth of free time for the Vasari fighter squadron to go around strafing enemy ships, 2 minutes of air superiority.
And, this is a simple fight between a lone Aeria Drone Host and a single Lasurak Transporter(both are carrier cruisers). This is without any support from capital ship abilities or cultural influence. Here are the bonuses they'll get from capitals/culture:
AdventHalcyon Carrier - The Amplify Energy Aura ability, at Level 3, will decrease cool-down time by 30% and increase damage by 30%, and the Adept Drone Anima will make for more fighters per squadron(I think 1 for every level added to the ability). The Halcyon's ultimate ability, Drone Tempest, will temporarily throw out huge squads of 17 drones each. Although a normal Vasari fighter squad can still defeat an Adept Anima fighter squad for the loss of 2 planes, it's best to run away when faced with a Drone Tempest and wait for the storm to finish.
Rapture Battlecruiser - The Concentration Aura ability, at Level 3, will give Advent strikecraft a 30% damage boost anywhere in the gravity well.
VasariCultural Influence - When operating in their own cultural influence, all Vasari weapons get an 11% damage boost.
Skirantra Carrier - The Repair Cloud ability gives all Vasari ships/structures/strikecraft within a constant free repair service. The Microphasing Aura ability, at Level 3, gives all Vasari strikecraft a 30% chance every second of teleporting 750 distance towards their target in no time, which allows them to rapidly close in for an attack pass or dodge enemy attacks. The Scramble Bombers ability simply throws up and extra squadron of bombers for a little while, and a maximum of two extra bomber squads can be scrambled at once. And the Skirantra's ultimate ability, Replicate Forces, allows it to use it's antimatter supply to instantly build a new frigate or cruiser - like a mobile factory. Anything built by this factory is a perfectly real ship which you can use permanently just like any ship built at a normal factory, so if you need an extra squadron up, you can build a new Lasurak Transporter.
Antorak Marauder - The Distort Gravity ability doubles the speed of all Vasari ships and strikecraft within range, so you could have fighters pulling speeds of >5800 units, and bombers exceeding 4000!
Stilakus Subverter - If a fighter/bomber squadrons target gets hit by the Subverter's Defeat Shields ability, the chance for the squadron's Phase Missiles to penetrate the target's shields goes up from 25% to 50%, and even if they don't get past the shields, shield mitigation is reduced by 10%.