Having not played all Jobs to their fullest (You only have four (SCH/PLD/SMN/MNK) of the nine jobs capped,) I really don't think you are one to say how they are different or not. A level 30 job/class plays quite a bit different than a level 50 one. Gear changes play style as well as overall abilities gained. You should perhaps cap the other jobs, and explore more how they are different in mechanics and play style before making anymore decisions there-in.