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
Villainous dungeon management game about luring monsters and crushing do-gooder heroes.

Optimization · Pure Optimization
A perk-driven sci-fi RPG won by flaw selection and dialogue routing.
Dungeon Keeper 2 leans Optimization (Pure Optimization); The Outer Worlds 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.
Dungeon Keeper 2
Slap-and-drop micro and possession combat need quick hands.
The Outer Worlds
FPS-lite with time-dilation aim
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Dungeon Keeper 2
Hero waves and rival keepers run on scripts.
The Outer Worlds
Scripted enemies
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Dungeon Keeper 2
Hero party timing and creature moods vary mildly.
The Outer Worlds
Loot rolls, dialogue check variance
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Dungeon Keeper 2
Dungeon layout, creature economy and research are solvable.
The Outer Worlds
Perks, flaws, dialogue routing rewarded
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.