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

Variance · Systems & Chaos
Careful descent through procedural depths balancing survival systems against permadeath.

Optimization · Practiced Mastery
Progressing through a contaminated open world by solving its scenario tech tree and optimising base builds.
Below leans Variance (Systems & Chaos); Once Human 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.
Below
Stamina-based combat punishes sloppy dodges and swings
Once Human
Third-person shooting and dodge rolls require real aim and timing
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Below
Creatures and the Darkness follow rules, not minds
Once Human
Deviant creatures follow scripted attack patterns only
Below leans a little harder on variance, though the gap is small.
Below
Procedural floors, traps and loot reshape every descent
Once Human
Deviant spawn composition and loot tables carry meaningful randomness
Once Human leans a little harder on optimization, though the gap is small.
Below
Survival crafting and trap knowledge converge with experience
Once Human
Scenario tech tree, base construction, and gear crafting are solvable
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.