It varies GREATLY.
Having an extremely well geared Scholar (Ix. Cloak, All Torques, HQ Staves, M.Acc Gear) and Black Mage (Morrigan's set, Af1 and Af2 +1's), as well as Novio, Moldavite, and Herald Gaiters; I find that the versatility of each job comes into it's own depending entirely on what you want to fight.
Simple case: Puddings. Now, I thought that the biggest problem with Puddings was that when they open with Thundaga3, you got no chance of surviving on Sch. Wrong, I just run to 30" and be out of range and continue. On Blm you can Stun puddings npnp. I find it easier and quicker and better exp solo on Sch which does less damage than my Blm which does more. Simply because Sch has them Strategems, mainly Parsimony and Alacrity for Puddings for MP conservation and quicker nukes/recasts.
I've solo'd Ix'Mnk on Sch, Blm and Cor (ya, lol), and in all honesty, I personally found it easier on Cor than Blm or Sch, but that aside, Sch/Nin gives you very LITTLE protection. It's all nice and dandy to have Cure4 and Reraise2, but not having Stoneskin or Gravity without /Rdm is an absolute Bitch when soloing stuff. Sch is kinda limited in this respect; for most effective soloing at endgame, Sch needs Rdm sub to be really awesome. Also, Sch doesn't get DoT spells similar to Blm, which are quick and easy to cast (Poison2, Choke, Burn, etc). Helix-spell'd DoTs are nice, but unreliable as far as the actual output of damage (The duration has a LOT to do with resistance, and on most NMs, you'll find that the damage is both initially shitty and doesn't last very long), and you'll find yourself in need to keep recasting the Helix spells over and over again, which will drain your MP, as well as the casting time...
Now Blm/Nin lacks Gravity and Stoneskin too, but makes up for it by the use of Stun. You can Stun a mob, run ahead a bit, and put Utsusemi up npnp before running again.
I haven't yet tried Limbus solo on Scholar. But I have done a hell of a lot of mob soloing on Scholar and I find it easier to solo regular mobs on Scholar than Black Mage. However, I like the extra spike damage Black Mage offers over Scholar because it kills things quicker, so when I do go off to kill NMs, I generally take Black Mage.
And as a Salvage leader, Scholar OWNS Red Mage and Black Mage in Salvage 10000000000%. It's such an amazing job. Unlike Rdm where it focuses on healing lost HP, Scholar prevents you losing HP, which makes things so much easier. Phalanxga, Stoneskinga, an Enblizzaga in Salvage lets you tear through mobs. Last night we did a 4 man Bee rampart and as the only mage, the bees were hitting for 0 dmg with Phalanx, Protect and obviously, Stoneskin. Sch's ability to heal and cure Salvage is phenominal, and I much prefer going Sch over any other job I have (Brd and Smn being my other 2) to Salvage. I've also taken Sch to Dynamis, and managed to keep cure an entire ALLY by myself (with the help of Refresh and Ballads, of course), but it is so easy to do if you know how to play the job. Sch in Einherjar rocks as a Pseudo-Whm too, and because of the damage prevention it offers, I like Sch far better than Whm when healing parties.
But all that aside, Blm is a lot harder to gear awesomely than Sch. Most of Sch can be bought or NM'd; Blm, however, needs to be Limbus'd, Dynamis'd, Salvage'd, HNM'd, Sky'd, and Sea'd. And it sucks that Sch gets so little out of endgame, when it offers so much.
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