X-2.

Leveling up jobs was simple and completely under your control.

You can change jobs at any point during battle.

With certain Garment Grids, doing so can even get you bonuses.

You can get really creative, to the point where even dresspheres you sorely underestimated can become very useful. I was surprised when I noticed how good the White Mage becomes in the postgame, if you use it right.