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Edit: Just tested it out with speedup, savegame editor and turbo button Master spheres:
The result is quite a difference:
Here are Tidus stats after activating every node via Master Sphere on the sphere grids
Standard Sphere grid // Expert Sphere Grid
Strength 187 // 109
Defense 160 // 141
Magic 147 // 169
Magic Defense 129 // 122
Agility 184 // 156
Luck 36 // 32
Evasion 134 // 70
Accuracy 80 // 77
The difference in maximum strength seems quite extreme, think I'll stick to the standard grid for this one...