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

Optimization · Light / Casual
A first-person horror about exploring a haunted Prussian castle.

Optimization · Light / Casual
Cyberpunk horror where a detective hacks the memories of the dying.
Amnesia: The Dark Descent leans Optimization (Light / Casual); Observer leans Optimization (Light / Casual).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Amnesia: The Dark Descent
Stealth and hiding, low demand.
Observer
Walking with brief stealth segments
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Amnesia: The Dark Descent
Monsters follow scripted patrols.
Observer
The stalker sequence is scripted
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Amnesia: The Dark Descent
Minor encounter variation.
Observer
Unknown story branches and apartment secrets
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Amnesia: The Dark Descent
Oil and sanity management is shallow.
Observer
Investigation logic and clue piecing
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.