Personal experience here.
With a few exceptions, Job's aren't that great in PvP.. Let's look at each Job vs. it's corresponding Class.
Warrior vs. Marauder - WAR like all Job's, gives you a nice stat boost to the stats that matter, namely Vit and Str. This is a big plus. But the rest of the WAR suite pales in comparison to what MRD offers you. First off you get Defiance, which is a 25% nerf to your damage done to access four amazing tanking skills that are situationally useful for DPS. See, the main issue with WAR (and PLD for that matter) is that people won't be attacking you. You're not a priority. You're so tanky just based off the plate-class armors that there are other, better targets to be concerned about (namely ARC/BRD and DRG's or MNK's).
So in this case, I feel that MRD is vastly superior to WAR because as a MRD you get access to almost all the same survival skills (everything but Inner Beast) while also increasing your cross class skill choices by double. This means you can turn your MRD into quite the damage dealer. Blood for Blood, Raging Strikes, Internal Release, Straight Shot and Berserk all add up to either a huge increase in damage when stacked together, or can be staggered to ensure you've always got higher-than-average damage. Adding in the usual survival skills of Second Wind and Convalescence makes it even harder to kill an already dense target. Toss in Virus and Feint for some general utility (don't knock a 20% slow effect for 10s, especially when it's the difference between getting a spell off or not) and you can affect the battlefield a helluva lot more on MRD than you can on WAR.
Final verdict? MRD > WAR. Sure, you lose out on AF and Relic gear, but you shouldn't be using AF, you should be in pvp gear. And while the loss of the Relic hurts, a Garuda or Titan weapon is more than enough to bring the pain when supported by your nearly-endless rotation of DPS cooldowns.
Paladin vs. Gladiator - Unlike MRD vs. WAR, this is a bit more of a wash. PLD offers some useful unique abilities with Cover and Spirits Within. Sword Oath provides good, steady damage that is tied to your auto-attack, meaning the AI takes care of it as long as you're in range, even for a fraction of a second. Furthermore, all the things you can potentially sub as a PLD are just great as far as pvp goes; Mercy Stroke for a finishing blow, Fracture for another DoT on top of CoS, Bloodbath and Foresight for extra survivability if it's needed, and Stoneskin because it'll give you an extra 10% of your life and let you use an MP pool that would otherwise go to waste. PLD functions amazingly as a support/peeler that can briefly amp their damage via FoF to help burst down targets. Furthermore, you get access to your AF and Relic, which if you have a lot of AF2 is generally enough to function until you get some pvp gear.
By comparison, GLD lacks the general utility the PLD brings, but makes up for it with a higher potential damage due to CCS's, much like MRD does. GLD can potentially put out a LOT more damage than PLD can, with the added bonus of widening the pool of MP-using skills you have access too. You can also keep some versatility via Feint and Virus, allowing you to debuff enemy players on top of your usual peeling/interference role.
Verdict - It's a wash. Depends on what you want; PLD is better at supporting your team and spoiling the enemy, as well as having access to some amazing starter gear. GLD can put out more damage than PLD, and trades the PLD unique utility for some utility of it's own. Whichever you prefer is a matter of what you think your team needs most.
Archer vs. Bard - Similar to GLD/PLD in a lot of ways, the major determining factor comes down to how useful you think songs are. With a BLM/SMN in your group, Foe's Requiem can help buff their damage immensely. Army's Paeon means you can turn MP into TP, allowing more mobility via sprint than is typical for a TP-based class. Aside from the normal Relic/AF comments, the only major decision is; do you want songs or do you want more cross-class skills?
In this instance, BRD would be more the utility/general DPS role, while ARC could be made significantly more survivable with the addition of skills such as Bloodbath, Foresight and Convalescence. And that's really the choice you're making; more group support via BRD, or higher survivability via ARC. You'll probably be best off looking at what your server cluster does in terms of strategy. Do they focus on the healer to the point in tunnel visioning? BRD might be best for the TP regen, ensuring your WHM or SCH always has TP to run (not to mention your team). Do they like to split damage between healer and a dps? Then ARC with more survival skills might be the way to go.
Verdict - much like with PLD vs. GLD, it's a matter of what you think you need more.
Black Mage vs. Thaumaturge - Again, Relic/AF accessibility applies here, as well as the innate job stat bonuses. The same argument made for ARC/BRD can be made here; do you find yourself under constant attack and in need of more survivability? Or are you largely left alone or CC'd and can get off a few casted spells every now and then? If the former, THM is probably the way to go; you get all the extra survival skills you could grab as a BRD and then some. Bloodbath works on spells, Keen Flurry and Featherfoot are both reductions to incoming damage (as is Foresight for that matter). Blood for Blood and Internal Release are great DPS additions, and you could even opt for Stoneskin for a bit more survivability/group utility (not that BLM or THM suffer from a lack of group utility).
In short, BLM will hit harder, but THM has access to a larger pool of cooldowns that will help you keep alive. Choose what works for you based on the same criteria highlighted in ARC/BRD above.
Verdict - basically the caster version of ARC/BRD.
White mage vs. Conjurer - Like MRD/WAR, only reversed; the job is distinctly better than the class. Any benefit of extra defensive cooldowns that could be gleaned by cross classing PGL or MRD skills is lost by not having access to Regen and Benediction. Bene is a final "NOPE!" button for when you or someone else is nearly dead, and Regen, especially with Divine Seal active, is the kiting WHM's best friend. Swfitcast Holy is great for some burst damage and an aoe stun, and that can sometimes be all you need to get off a Cure 2 or Medica 2.
While CNJ could potentially offer something with the variety of cross class skills available (particularly if you wanted to be a "DPS" CNJ), I don't see the tradeoff as being worth it. There's probably going to be someone who makes DPS CNJ work with some kind of insane rushdown style of group play, with the goal of making sure more of them are dead before you go down, but the state of CC in this game really throws a monkeywrench into that idea. A single sleep on a character who has blown all their DPS cooldowns for a big burst renders the whole thing wasted. Even with Purify the next sleep is going to be 15s of snooze time, and the power of this start is predicated on your enemy standing nicely in the open while you cast and not being a meanie who attacks you and stuff.
Verdict - WHM outdoes CNJ by a good margin. Maybe the meta will change in the future and allow a DPS CNJ, but that's the future.
Scholar vs. Arcanist - Absolutely no question. SCH all the way. All the normal Relic/stat/AF notes apply, but this time you get a mobile healing bot that has an aoe regen that goes through walls, amazing heal/shield skills, great utility with Miasma II and Ruin II, and the ability to instantly heal someone for 25% of their life three times per minute. Between your Lustrate, your pet, your shields and your debuffs, there is no combination of CCS's that will be greater than your unique job skills. None. Don't even think about it. Besides it wouldn't make any sense, because if you have SCH at 50, you have SMN at 50, so if you want to DPS with a pet, switch to SMN.
Verdict - it's not even close. SCH all the way. ALL OF THE WAY. Most importantly, and this is *REALLY* key....LUSTRATE DOES NOT OBEY HEALING DEBUFFS. Think about that.
Summoner vs. Arcanist - more or less the same rules apply as SCH/ACN, only not quite as....vehemently. While you can make an argument for the survivability and utility found in CCS's, SMN doesn't really hurt for utility, and having a few instant cast DoT's to pull from goes a long way in an environment where people will be LoSing you contantly. Add this to your upgraded pet abilities (Titan or Ifrit is better than Garuda thanks to the LoS issues) and it's again a no-brainer. While you can technically get more survival stuff from CCS's, it's not worth the loss of your unique stuff. Don't underestimate the power of a Tri-Disaster/Blizzard II combo to pin melee in place for a little while.
Verdict - SMN. Just SMN.
Monk vs. Pugilist and Dragoon vs. Lancer - I put these two together because, well, they're nearly the same. Both MNK and DRG offer unique Job skills that are key to performing well in pvp. Dragonfire Dive, Spineshatter Dive, and Shoulder Tackle are all necessary to stay in contact with enemies, and the stat boosts from being a Job instead of a class are just the icing on the cake. You have all the necessary CCS's in your main classes to boost survivability and damage, in addition to your own trait-buffed native cooldowns.
As with SCH, any gain from staying the class and taking more CCS's is vastly outdone by the gear, stat and Job skills gained from being a Job.
Verdict - Get hopping. Or tackling. DRG and MNK all the way.
Edited, Dec 19th 2013 3:33pm by Quor