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

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.

Optimization · Pure Optimization
Experimenting with whimsical screens until their hidden interaction logic clicks.
Portal leans Optimization (Pure Optimization); Samorost 2 leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Portal
Portal placement timing modest.
Samorost 2
Pointing and clicking has no dexterity component
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Portal
No adversary modeling player.
Samorost 2
No opponent of any kind exists
Samorost 2 leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
Samorost 2
Surreal puzzle logic is hidden until experimented with
Portal leans clearly harder on optimization.
Portal
Pure puzzle-solving optimization.
Samorost 2
Each screen is a small solvable interaction puzzle
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.