As I have said elsewhere, this sword is roughly equivalent to one-half a normal-quality staff in terms of accuracy (high-quality staves have been demonstrated to give approximately 30 Magic Accuracy). This is... extraordinarily non-trivial. The only jobs with native access to an area-of-effect-based Sleep are Bard, Black Mage, Scholar (with stratagems) and Blue Mage (and Summoner, I guess...). Black Mage, in particular, can afford to really pile on Enfeebling Magic gear, but their access to pure Magic Accuracy pieces is limited. Blue Mage, on the other hand, can dual-wield these swords, and along with +20 Skill in gear, +10 Magic Accuracy from merits, and the plethora of Magic Accuracy in gear, can land unresisted Sleeps when they are called for. Of course, given the awkward area-of-effect, high recasts, and the fact that all other sleep spells will overwrite Blue Magic Sleep spells, these spells would be support at best whenever a Black Mage is present. For passable DPS and DMG and a whooping +60 MP, these swords provide Blue Mages with the potential to damage deal without having to awkwardly switch into staves, or perform a full gearswap just to cast Flash. Spells that are not INT/MND/CHR or MAB dependent (most Debuffs and Breath Spells) are greatly enhanced by this sword.
An extremely underrated and unpopular sword at present. Most people working on sword trials have dove straight into Antea or the Elemental paths without appreciating the utility of this sword. By comparison, the next highest damage sword would be Concordia at 46 base damage. While Concordia has several unique evoliths to enhance weaponskills or other situational effects, its crippling 268 delay brings its DPS to approximately 10.3, lower than Beastslayer. Concordia is not a DPS weapon; it is a spike damage/weaponskill-based weapon. The Nobilis offers a graceful option for the Blue Mage seeking to preserve their DPS as well as their weaponskill damage. At a high (and constant) 11.9 DPS and massive 47 base DMG, the Nobilis is one of the most balanced swords currently available. Though it doesn't add much other fluff, like attack or accuracy, it remains a solid weaponskill/DPS sword for the mainhand without the TP dependence of Perdu and with a superior weapon rank.
Everybody's favorite and with good reason. At a glance, this sword may not look like much. With base DMG:40 and 264 delay, it has extremely poor DPS and DMG given its base stats alone. However, its ~40% processing rate of "occasionally attacks twice" gives it an adjusted DPS of 12.7, and of course boosts its already-high relative TP gain. This weapon is an ideal offhand for a majority of situations. More TP means stronger weaponskills and, by extension, stronger overall skillchain damage, but that's not what I find most attractive about it. Better TP gain for Blue Mages implies more opportunities to use TP outside of Chain Affinity, and thus, less reliance on MP-based forms of damage-dealing. A weapon like this, with proper TP and WS gear/spells/traits, could greatly incentivize setting up skillchains with other players or using Vorpal Blades as a primary form of damage dealing, saving MP and set points for other, more salient spells and traits. Take note that killing 5-10 Lord Ruthvens is no small task... I personally will wait until I have any chance in hell before I prepare a Schiavona for this trial.
For RDMs and PLDs considering the Antea, stick with your Joyeuse. Joyeuse has an adjusted DPS of 13.6, piercing damage and considerably lower delay. In offhand, that means quicker attacks, faster TP, and better DPS. For PLDs, quicker TP gain for Atonements is likewise superior. The only reason I could see to make Antea for these jobs would be to have 2 "Occ. Atk Twice," weapons which is kind of silly. The TP fed to the mob, as well as the poor base damage of the mainhand (relative to other options), undercuts the utility of the Antea.
The Fire and Thunder path Swords are solid offhand options. The Fire path mostly replaces Perdu and provides another Blue Magic damage tier. The Thunder path provides a huge +10 physical accuracy in total, with the added bonus of DEX for spell mods and critical hit rate. However, I personally believe that Blue Mages should choose one of these swords, unless they happen to already have a Koggelmander. The Fire path in particular is attractive when /THF and against beast enemies (due to the Lizard Affinity of Koggelmander), but the Thunder path is nice for Elvaans or Blue Mages uncomfortable with their physical accuracy.
I would caution Blue Mages against focusing only on these swords. Though solid options both in their own right, these two swords lack what the Nobilis and Antea provide that cannot be furnished in other slots. ATK, STR, DEX and ACC can all be obtained via food, gear or traits, while base damage and delay cannot. For situations in which damage dealing is lower priority, other swords come into play, but when sword DPS counts, you should look beyond a few STR or DEX and beyond the "big three."