head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is reads, and it is a single point.

Optimization · Practiced Mastery
A real-time RPG carried by ascension-grid routing and magic crafting.

Optimization · Practiced Mastery
Action-RPG combat where the panel-grid loadout puzzle matters more than reflexes.
Final Fantasy XV leans Optimization (Practiced Mastery); Kingdom Hearts 358/2 Days leans Optimization (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Final Fantasy XV
Real-time combat, modest input demand
Kingdom Hearts 358/2 Days
Real-time keyblade combat with modest timing demands
Final Fantasy XV leans a little harder on reads, though the gap is small.
Final Fantasy XV
Scripted enemies
Kingdom Hearts 358/2 Days
Heartless and bosses run fixed patterns
Final Fantasy XV leans a little harder on variance, though the gap is small.
Final Fantasy XV
Loot and ascension variance
Kingdom Hearts 358/2 Days
Loot drops add minor randomness to gearing
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Final Fantasy XV
Ascension grid, magic crafting, party planning
Kingdom Hearts 358/2 Days
The panel grid system rewards careful build planning
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.