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

Optimization · Practiced Mastery
Routing scripted patrols with vampire teleports and a light skill-build layer.

Optimization · Practiced Mastery
Breezy open-world adventure romping through Greek myth puzzles and monsters.
Dark leans Optimization (Practiced Mastery); Immortals Fenyx Rising 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.
Dark
Shadow-teleport timing matters but combat is clunky-forgiving
Immortals Fenyx Rising
Dodge timing and aerial combos
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Dark
Guards run scripted patrol and alert routines
Immortals Fenyx Rising
Mythic beasts follow fixed movesets
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Dark
Patrols are fixed once observed
Immortals Fenyx Rising
Little randomness in the open world
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Dark
Skill builds and patrol routing solve each stealth arena
Immortals Fenyx Rising
Vault puzzles, gear builds, and stamina routing
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.