Depends on how much time you are willing to invest in the game again.
Because I myself can put the time into Final Fantasy games and I'm a grinding masochist anyways, I tend to make my characters as powerful and as early in the game as possible. Sure it may ruin and make make things too easy in later stages, but then thats how personally I play it.
So my own personal vote would go for equal. In the end it depends on you.
Yeah back in the FFVII/FFVIII days, there were times where I would be really stupid and end up getting my main/favourite characters to the maximum level even on Disc 1.Thats exactly how I play FF games, There are always points where leveling up is easy, so I spend more time there than most people would, then through the game you are always a level ahead..
I never took it to max early on, just enough to give an edge and the occasional top up through the game.
FF XII is even easier to do this on with the bonus you get for continually killing the same kind of enemy over and over.
IIRC FF8 was the easiest to level your toons up to max (100?) as there was some kind of weird exp system whereby you got the same exp for killing a creature at level 99 as you got at level 2, so you could just grind on the same low level mobs...could be wrong tho as it was a long time ago. Anyone confirm?