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

Optimization · Pure Optimization
The genre-defining loot ARPG whose builds, runes, and trade economy players still optimize decades later.

Optimization · Systems & Chaos
PS1 virtual-pet RPG where you raise, train, and evolve a Digimon whose growth follows hidden rules.
Diablo II leans Optimization (Pure Optimization); Digimon World leans Optimization (Systems & Chaos).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Diablo II
Positioning and potion reflexes, little else physical
Digimon World
Light real-time battle nudging and timing
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Diablo II
Monster AI is fully mappable
Digimon World
No adaptive opponent anywhere
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Diablo II
Loot RNG and random maps drive the grind
Digimon World
Hidden evolution requirements and care mistakes dominate early play
Diablo II leans a little harder on optimization, though the gap is small.
Diablo II
Builds, breakpoints, rune economy, magic-find routing are the game
Digimon World
Once requirements are mapped, raising becomes a solvable schedule
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.