The best capitol ship is the one that best helps you implement your overall fleet strategy. That could be Tarkin, Ackbar, or Mace depending on different factors we will outline below.
However, if you don’t have a real strategy, and you are just using whichever ships are the most powerful, it is kind of a toss up between Ackbar and Mace.
–Ackbar is probably your best bet if your best ships are evenly distributed between factions and/or more attacker based.
–Mace is probably your best bet if your best ships lean a little to the tankier side and/or you are using a few republic ships (rex, fives, plo, ahosoka, JC, etc).
–Tarkin’s Executrix is a lot better than people give it credit for. But you need to have a targetlock/debuff strategy and/or Empire ships to make it shine. Otherwise, it is easily the worst of the three.
As for me personally, I am using a target lock strategy. My starting lineup is Vader, TFP, FOTP, Biggs, and Maul. Then my reserve is in this order: Fives, Boba, GS. The concept is TFP and FOTP are fast and can put target locks on right away. This causes Biggs to taunt. Then the enemy goes and damages Biggs. Next Vader goes and target locks someone which recovers some of Biggs protection keeping him alive. Then maul puts his retribution on Biggs, which gives him some bonus protection. I am currently using Ackbar’s Homeone ship. This means Biggs will continue to get extra bonus protection everytime he attacks out of turn, this basically makes him invincible while he has retribution up (as long as the enemy isn’t stealthed). While this is going on, my other ships are target locking opponents, and FOTP is getting lots of turns and damage. When Biggs finally goes down, Fives comes in and mega blasts all the target locked people. It is pretty much over at this point.
I think Ackbar works really well here for a capitol ship. However, I do think Tarkin’s Executrix has much damage potential, and could possibly end the fight a lot earlier due to all the target locks going around and the additional damage from all those debuffs/target locks.
I don’t think this strategy would work as well with Mace, but it might because of all the turns being generated, he would get a lot of capitol ship turns. He could also taunt up Fives after Biggs goes down, which could really help mid fight. He also brings other things to the table like being able to inflict target locks himself, and aoe hitting target locked enemies. But overall, I think Ackbar and Executrix are the best for implementing this strategy.
Ackbar makes biggs last longer from his passive, and the additional assists he generates means more potential for target locks (further protecting biggs), and more hits on target locked enemies giving FOTP more turns. Also, when Fives comes off the bench, he has a guaranteed critical hit with his mega blast on all the target locked enemies.
Executrix, while not doing anything to protect Biggs, would simply grant way more damage output. This would eliminate enemies faster, and when Fives does come off the shelf, his big hit, while not being a guaranteed crit, would hit almost as hard when not criting, and WAY harder if it does crit.
The point of my particular strategy example here is to show that the best capitol ship is the one that helps you implement your strategy the best.
That is my wall-of-text novella on fleet strategy and which capitol ship is best. Hopefully, it can help some of you who are looking for fleet advice. For what it is worth, I am placing in the top 3 routinely now in a “Super Whale” fleet arena shard. Nearly everyone in the top 75 of my fleet arena has fully maxed out ships (except me). I mean every ship is 7star, level 85, with fully maxed out character crews, including the capitol ships. Many have 7star TIE Advanced and 6/7star TIE Reaper ships. There are people with OVER 176k ship power, and I would say the average ship power for the top 50 is 165k. I only have 158k power level, and none of my ships are fully maxed yet. Yet, I am still able to place somewhere in the top 3 each day.
Having a fleet battle strategy, and selecting the capitol ship that best implements that strategy, can allow you to really punch above your weight class.