head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Optimization · Pure Optimization
A number-stacking playground where grinding and build optimisation dwarf everything else.

Optimization · Pure Optimization
A pure optimization exercise where sphere grid planning and boss weakness exploitation defines mastery.
Disgaea 4 Complete+ leans Optimization (Pure Optimization); Final Fantasy X leans Optimization (Pure Optimization).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Disgaea 4 Complete+
Turn-based menus - hands are never the bottleneck
Final Fantasy X
Fully turn-based; zero time pressure on inputs
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Disgaea 4 Complete+
Enemy AI is fixed scripts, never models the player
Final Fantasy X
All aeons and fiends operate on fixed AI scripts
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Disgaea 4 Complete+
Item World layouts and drops randomise but average out
Final Fantasy X
Minimal RNG in base game; overdrive gauge charges predictably
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Disgaea 4 Complete+
Stacking multipliers into million-damage builds is the entire endgame
Final Fantasy X
Sphere Grid routing and break damage limits make the game theoretically solvable
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.