I don't want to type everything out, otherwise I'll be here all night, so I'll try to condense my comparisons and give my two cents. Please share your comments and thoughts on the subject with me or maybe open my eyes to something I'm not seeing.
3rd Level
(Devotion)
Sacred Weapon is a monster imo. +CHA to attack rolls for 1 minute... Couple this with the Great Weapon feat and just go to town on people...
Turn the Unholy is situational based on foes being fiends or undead, but undead are relatively common in most games I would think...
(Ancients)
Natures Wrath seems pretty lackluster to me... A single target within 10 feet restraint... STR or DEX save... Probably gonna be escaped in most situations.
Turn the Faithless is about on par with Turn the Unholy, it really depends on your campaign.
(Vengeance)
Adjure Enemy is nice because it can be used on any creature type. However the trade off is its only for one target.
Vow of Enmity is pretty nice, but only works on one creature...
IMO this round goes
Sacred Weapon > Vow of Enmity > Natures Wrath
Turn/ Unholy = Faithless > Abjure Enemy
7th Level
(Devotion)
Aura of Devotion, immunity to charm. Can't go wrong with an always active immunity that you can radiate to others. Mileage may vary based on if your enemies can even charm you.
(Ancients)
Aura of Warding, resistance to damage from spells. IMO this is pretty badass. All spell damage cut in half AND you can radiate the ability to others as well.
(Vengeance)
Relentless Avenger lets you move up to half your speed following an AoO you hit someone with, this movement doesn't provoke any AoO's of its own. I don't really know how to feel about this... I personally find it a little lackluster for a lot of different reasons I won't explain unless someone asks me to.
IMO this round goes
Aura of Warding > Aura of Devotion (because it's always active) > Relentless Avenger (situational and meh...)
15th Level
(Devotion)
Purity of Spirit's mileage may vary based off the amount of evil/good you are fighting, but I think a permanent aura to protect vs good/evil is pretty beefy.
(Ancients)
Undying Sentinel, I like the utility of this ability simply allowing you to stay in the fight longer. No aging drawbacks is a nice flavor touch.
(Vengeance)
Soul of Vengeance... ok this is probably where this Oath really chaps my ass... This skill sucks IMHO. The main reason is that it is solely reliant on you still having your Channel Divinity Vow of Enmity available. Every other Oath's abilities of this level are completely seperate from the channel and not reliant on it.
IMO this round goes
Purity of Spirit > Undying Sentinel >>>>>>>>>>>>> Soul of Vengeance
20th Level
(Devotion)
Holy Nimbus, 10 dmg per turn is pretty minor at this level, but its every enemy within range for every turn, so I like this. Plus if they're fiend or undead you get advantage on saves against their spells. Mileage may vary on the second part.
Elder Champion, HP regen is nice. However I typically don't see many paladins go heavy on the spell casting side of the house, especially now that our spells fuel our smites. Aside from the HP regen I find this rather meh...
Avenging Angel, this is neutral for me. Sure you can fly for 60 ft and give off a fear aura, but once you hit your enemy the fear is broken. I suppose it could be used to great effect if you meta game and your whole group focus fires every frightened enemy one after another. I see this more as an "oh 
IMO this round goes
All about even I suppose...
Alright, so that's my two cents on this matter. Personally I was hoping to like the Vengeance Oath a lot more than I do, simlply because it opens a lot of role play options that we're hard to do given the strict alignment codes of the past. However, I can't help but feel this Oath is lackluster.
What does everyone else think?
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