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

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.
Optimization · Pure Optimization
A two-player co-op puzzle game solved entirely by describing what you see over voice.
Portal 2 leans Optimization (Pure Optimization); We Were Here leans Optimization (Pure Optimization).
Portal 2 leans clearly harder on execution.
Portal 2
Portal placement requires some precision but timing is lenient.
We Were Here
Walking and talking; no dexterity test
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Portal 2
No opponent; puzzles are static.
We Were Here
Your partner cooperates rather than opposes
We Were Here leans clearly harder on variance.
Portal 2
Puzzles are deterministic with no randomness.
We Were Here
Each player sees only half the puzzle's information
Portal 2 leans clearly harder on optimization.
Portal 2
Solving the puzzle's logic IS the entire game.
We Were Here
Puzzles have fixed solutions once communicated
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.