head to head
Neither is simply harder - they are hard in different places. Mind Snares: Alice's Journey demands more variance; Portal 2 demands more optimization.

Optimization · Pure Optimization
A hidden-object puzzle adventure solving fixed logic chains through a dream world.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.
Mind Snares: Alice's Journey leans Optimization (Pure Optimization); Portal 2 leans Optimization (Pure Optimization).
Portal 2 leans clearly harder on execution.
Mind Snares: Alice's Journey
Point-and-click pace, no motor 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.
Mind Snares: Alice's Journey
Solo puzzle adventure with no adaptive opponent
Portal 2
No opponent; puzzles are static.
Mind Snares: Alice's Journey leans clearly harder on variance.
Mind Snares: Alice's Journey
Hidden-object placement randomized lightly per scene
Portal 2
Puzzles are deterministic with no randomness.
Portal 2 leans clearly harder on optimization.
Mind Snares: Alice's Journey
Solving fixed puzzles and logic chains is the whole game
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.