In the PSX version, any level above 50 will probably be unnecessary to attain, unless you are purposefully trying to max out your characters. You can beat the game around 35 rather easily. Level 40 would be a cakewalk.

In the GBA version, you do not need to grind much. I cannot remember how high my levels were by the end of the game, but I'd guess they were hovering around 55 without grinding. Your characters grow much quicker in that version as well.

Comparing the two is like comparing apples to oranges. Too many variables between the two versions.