I can't decide which would be better. I am trying to form a decent FSC loadout. My current equipment is Nameless Set, Grey Owlite Shield, Umbra Driver, and Gigawatt Pulsar(Which will become Polaris eventually)
Antigua vs. Sealed Sword
I am the lead gunner in my guild. Soooooooooooo. I got Antigua. Now... AP line or Sentenza line?
I would recommend getting the AP first; it has a little more utility at present. There is potential for the damage types for the Peacemaker and Sentenza to be changed to elemental and shadow respectively, dropping the piercing damage.
A current thread started by the game designers discusses the possibility that Argent Peacemaker and Sentenza will have their damage types changed to pure elemental and pure shadow. I would not commit to any Antigua line until this shakes out.
If they are changed, then they will be redundant with your Polaris and Umbra. If they are not changed, then they will remain split-non-normal-damage weapons, which are undesirable.
You have a shadow gun and an elemental gun. The obvious thing to do now is to get a piercing gun (Callahan, Blitz Needle, Plague Needle). Then you'll have your three damage types, and you'll have no use for any Antigua-line gun.
I agree with Kilbride that Polaris seems to work well in FSC. The knockback helps with clearing crowds of monsters (unless you clear them into your teammates).
Your Pulsar already has ranged attacks covered - the expanded shots and knockback are useful on FSC, which is filled with zombies. The AP doesn't knock enemies back, nor does it do a significant amount of damage per shot.
If you are going to make a Polaris, I would recommend getting the Sealed Sword over the Antigua. I personally use the Argent Peacemaker but I have seen quite a few people using the Polaris to good effect in FSC. As having both could be redundant, you might use your tokens to get the Sealed Sword and upgrade it to the Divine Avenger, which is also a good weapon for FSC.
Sounds like you're a serious gunner, tho'. If you wanted both guns, you could do that too.