head to head
Neither is simply harder - they are hard in different places. Portal demands more execution; Secret Files 2: Puritas Cordis demands more variance.

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

Optimization · Pure Optimization
Deducing scripted inventory-puzzle chains through a conspiracy story.
Portal leans Optimization (Pure Optimization); Secret Files 2: Puritas Cordis leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Portal
Portal placement timing modest.
Secret Files 2: Puritas Cordis
Clicking hotspots requires no dexterity
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.
Secret Files 2: Puritas Cordis
Story characters are fully scripted
Secret Files 2: Puritas Cordis leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
Secret Files 2: Puritas Cordis
Puzzle solutions are hidden until uncovered, then static
Portal leans clearly harder on optimization.
Portal
Pure puzzle-solving optimization.
Secret Files 2: Puritas Cordis
Inventory logic chains are fully solvable with deduction
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.