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 narrative horror game tested primarily by puzzle knowledge and sanity-resource management.

Optimization · Pure Optimization
A charming JRPG carried by familiar evolution and party-build routing.
Amnesia: Rebirth leans Optimization (Pure Optimization); Ni no Kuni: Wrath of the White Witch 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.
Amnesia: Rebirth
Stealth and evasion; no real twitch demands
Ni no Kuni: Wrath of the White Witch
Hybrid action-turn combat, low input demand
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Amnesia: Rebirth
Enemies patrol fixed routes; no adaptive opponent
Ni no Kuni: Wrath of the White Witch
Scripted enemies
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Amnesia: Rebirth
Some encounter timing has variance; story rooms are fixed
Ni no Kuni: Wrath of the White Witch
Familiar catch and drop rolls
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Amnesia: Rebirth
Resource management, narrative puzzles and safe-path knowledge are solvable
Ni no Kuni: Wrath of the White Witch
Familiar evolution and party 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.