I choose the Sphere Grid.
The License board was too generic and too easy and you did not really need any strategic approach to enhancing your characters identity. It paved the way to make everyone into clones. Although I know you don't have to make them into clones but the possiblity is there.
Where as the sphere grid you had to plan more strategically or you'll end up wasting valuable moves. Why i say the sphere grid is more strategically challenging is simple:
1. You need different type spheres to enhance not only the characters abilities, but also the Aeons as well. If you lack some spheres, you have the option to fight monster creations to get the spheres you need. Or you can buy sphere distillers and cast them onto fiends to get the spheres you need. PLanning and strategy! I love it!
Who ever said there's a lack of spheres even when upgrading your Aeons is totally wrong.
2. If you want to make clones, this will be challenging since pathways start off differently. So in the beginning the roles and abilities of each character start off differently. Thus when you do battles, you need to strategize (is this a word?)and re-think your every encounter. Unlike in FFXII, you can buy axes for everyone in one setting. Boring!!! I would rather find a plan and strategy that works instead of saying "Hmmm.. I can't beat this boss! I'm just gonna buy 'Save the Queen' for everyone. MUahahaha!"
Don't even mention the different Weapons and Armor customizations!! So my 'Dragonkiller' sword may be different than yours! or I can even make 2 or 3 Kotetsu's each with different uses depending on the battle.
3. If you want a certain character to have an ability not obtainable from his/her starting position you can always use teleport, friend, return spheres. (Ex. My Auron can cast Holy) But you have to plan it out first before using, or else waste an uncommon sphere. More planning and strategy which I love!!
4. And in FFXII, you can't really go deep into leveling and customizing since there is no Break HP, Break Damage, Break MP abilities. So although more versatile, no matter how strong your weapons or strength abilities are, you'll only get up to 9,999 damage. Boring!!
In FFX, the game continues to encourage you to get your characters as much damage potential as they can get.
5. Should I even include the level unlocking spheres needed?? More planning!
All in all to sum things up, I love the Sphere grid since it involves more challenging strategic thinking than the License Board.
They should have called it the "License Bored." lol
