head to head
Neither is simply harder - they are hard in different places. Oxenfree demands more variance; Portal 2 demands more optimization.

Optimization · Pure Optimization
A supernatural teen drama where dialogue timing shapes relationships against a fixed mystery structure.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.
Oxenfree leans Optimization (Pure Optimization); Portal 2 leans Optimization (Pure Optimization).
Portal 2 leans clearly harder on execution.
Oxenfree
Radio tuning and walking demand no physical skill
Portal 2
Portal placement requires some precision but timing is lenient.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Oxenfree
Supernatural narrative with scripted ghost behaviour
Portal 2
No opponent; puzzles are static.
Oxenfree leans clearly harder on variance.
Oxenfree
Dialogue timing creates minor branching uncertainty
Portal 2
Puzzles are deterministic with no randomness.
Portal 2 leans clearly harder on optimization.
Oxenfree
Relationship and dialogue choices converge toward fixed endings
Portal 2
Solving the puzzle's logic IS the entire game.
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.