If I have to pick, then I'll go with freedom. However I can completely understand the restriction of that freedom should characters have fixed classes in the game or alternatively if jobs are affected by storyline.

I generally prefer the games where there are no fixed jobs as I would like to be able to have my favourite characters in my battle team and adjust them to fit. However, one way around this would be to have fixed jobs, but at the same time have them not be able to change once they are assigned a job. This would dramatically increase replayability, too - although I imagine balancing would be insanely difficult for Square Enix if they ever opted to do this.