From one who has touched the cart based FF series and dabbled with 7, did 9, and suffered most of 10... I'd have to say it's got to be the hardest or damn near it.
If you want a decent easy warmup try FF4Advance as it's got a stellar story, about 20hours long, set party with no job swapping/management, and the boss fights aren't as sadistic.
If you want a decent easy warmup try FF4Advance as it's got a stellar story, about 20hours long, set party with no job swapping/management, and the boss fights aren't as sadistic.