They serve their own goals, of course. I'd like to remind you we have a dedicated forum called The Arsenal for these subjects. Please move it there (without a shadow copy) because eventually an Admin will do it for you.

Vog Cub / Snarbolax

Special defense: Snarbolax.
Elemental is more prolific, but shadow creatures have some of the most difficult to defend against moves in the game.
Resistance: Vog Cub.
Freeze is annoying and poison is too, but Vog Cub's fire resist shines in Firestorm Citadel where everything and their grandmother sets you ablaze. It's one of the best places to farm crowns in the game.
Special bonus: Snarbolax.
Items can have good ASI UV's, but their damage bonuses are always specifically against one monster family. Trinkets, Skolver, Snarbolax and the Barb Thorn Shield are some of the few sources that have global sword damage bonuses you can't get on weapon UV's.

You cannot get the snarbolax without doing the insanely hard shadow lairs, if you don't already have Vog Cub or Skolver this will be very, very hard for you. Get Vog Cub for FSC, where you can farm crowns.

Divine Avenger / Gran Faust
Both have areas where they shine.
Do you like Royal Jelly Palace? - Gran Faust
Do you like having a small advantage in lockdown (curse, shadow damage)? - Gran Faust
Do you like having the chance to curse monsters on the second swing? - Gran Faust
Do you like using charge attacks? - Divine Avenger
Do you prefer more damage against undead/construct, which are more dangerous and common? - Divine avenger

Overall people will advise you get the Divine avenger since it's good in FSC.

Argent Peacemaker / Sentenza?
Ask that question in a few days/weeks, their damage might change soon.

Barb thorn / Final Flourish
They only have a different charge attack. I prefer a final flourish, it does 3 quick hits with almost double damage on all of them and a pretty wide area of effect. It one-shots menders and groups of gremlin Thwackers. It's a lot harder to use though.
Barb thorn has a "shotgun" like effect of shooting needles. It's much more user friendly and better in lockdown than the final flourish. Most people think it looks cooler too (even though I prefer the final flourish, I agree).
No sword is better, but it comes down to user preference.

Edit:
Polaris / Super Nova

Polaris on anything except gremlins (you don't want to shoot beasts as a swordsman anyway). If you get a Final Flourish, just spam the charge attack and you'll be fine. It almost one-shots any gremlin and interrupts their attacks.

this is pretty much a matter of preference
vog cub is preferred by the general community
divine avenger is generally better for pve and gran faust for pvp
argent peacemaker since sentenza's piercing/shadow doesnt do a lot for mainstream runs in the clockworks
Barbarous thorn blade for the thorns it spreads with its charge

Boxers, of course.

on the great editor debate, ed. Hands down.