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

Optimization · Pure Optimization
A noir sci-fi adventure weaving two storylines toward one memory-bending twist.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.
Gemini Rue leans Optimization (Pure Optimization); Portal 2 leans Optimization (Pure Optimization).
Portal 2 leans a little harder on execution, though the gap is small.
Gemini Rue
Light cover-shooting sections need minimal timing
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.
Gemini Rue
Enemies are scripted, never adaptive
Portal 2
No opponent; puzzles are static.
Gemini Rue leans clearly harder on variance.
Gemini Rue
Story twists and solutions unknown only on first play
Portal 2
Puzzles are deterministic with no randomness.
Portal 2 leans clearly harder on optimization.
Gemini Rue
Puzzles have single fixed solutions; walkthrough trivializes
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.