The foremost appeal of jobs is the unparalleled degree of specialization they offer. Their potential is best realized in party situations, where having well-defined roles is the key to success. There can be no doubt that jobs shine the brightest in the company of others.
Perhaps I always assume ARR will be semi-identical to FFXI and treat "JOBS" in ARR as "advance jobs" in FFXI.
with the explanation above, are we able to level the classes as high as the jobs and be as effective as jobs?
Classes are essentially free-for-all. You can swap and match abilities as needed to create your very own "class" within the weapon you choose. They're very loose definitions of what you can be.
Jobs are focused specializations within the weapon you choose. For example, iirc in 1.0 Paladin job required you to achieve level 30 in Gladiator and level 15 in Conjurer. I *believe* you were limited to selecting skills to *only* from Gladiator and Conjurer with perhaps some in Marauder (as well as the abilities you innately get from choosing Paladin).
The classes are what you would use out in the world because you can custom design them to your liking, but the jobs are defined roles that you would decide upon when joining a group in a dungeon (or party-leve farming, etc.). You don't level the jobs: the job levels are defined by the base class that particular job is associated with. Jobs are primarily for party play because they're a defined role that is more enhanced than the base class.
The "advanced jobs" in FFXI are misnomers because all jobs are 'equal' and they're not really any better than the original 6 you can get. Edited, Jun 14th 2013 12:04am by Viertel