I'll stick up for the License Board since I never cared for the Sphere Grid system. I don't think the Sphere Grid system is bad mind you, rather I just didn't think it was some great system template that every FF should follow. Of anything, it taught me how tedious leveling really is...

I prefer the License Board cause it is far more excessable and allows you to create the job class system (The system I really love) for your party. The board is smaller than the Sphere Grid but it allows for deeper customization. In FFX, by the time your party finishes the initial path of there character (usually end game) , they really don't need to go any farther in the grid except to level to fight optional creatures in the Monster Arena. On the otherhand, when you complete the License Board, you gain access to customize your party however you see fit and you can even change their customizations within battles which gives you a better strategic edge.

It's just more versatile and offers deeper customization IMHO.