The differences are:
- There is no predefined road to take. In the standart grid, each character, except Kimahri starts on place in the grid that has abilities tied to their own unique characteristics. Due to major grinding you could get those skills in every character, but a player doing only the main story, would get the predefined skills for those characters. Lulu get's the black magic, Yuna gets white magic, Auron gets warrior skills, etc etc.
The expert grid doesn't have such predefined paths. You can make your characters be whatever you want them to be, and the skills are mixed, so you can learn a white skill sphere and in the next level up you could learn a warrior skill.
- The Expert Grid has less Stat Spheres, which severely limits you high stats characters. To get 255 in each stat, you have to sacrifice HP or MP, in my case, i had to sacrifice 10 +500 HP spheres and 6 +50 MP spheres, putting my max HP at 59K and max MP at 900 MP. That is a severe hinderance when you fight the last dark aeons and Penance, unless you rely exclusively on Yojimbo's Zanmato.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
