head to head
Portal 2 asks more than Antichamber, and the gap is execution.

Optimization · Pure Optimization
A non-Euclidean exploration puzzle testing your willingness to abandon assumptions about space.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.
Antichamber leans Optimization (Pure Optimization); Portal 2 leans Optimization (Pure Optimization).
Portal 2 leans clearly harder on execution.
Antichamber
Navigation has no twitch demands
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.
Antichamber
No opponent; solo non-Euclidean exploration
Portal 2
No opponent; puzzles are static.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Antichamber
World is deterministic once its rules are understood
Portal 2
Puzzles are deterministic with no randomness.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Antichamber
Deducing the non-Euclidean spatial logic and gun mechanics governing each room
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.