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

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

Optimization · Pure Optimization
Methodically dissecting intricate puzzle boxes whose mechanisms are fully solvable.
Portal leans Optimization (Pure Optimization); The Room Three leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Portal
Portal placement timing modest.
The Room Three
Rotating and prodding mechanisms takes 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.
The Room Three
The Craftsman is narrative dressing, not an adaptive mind
The Room Three leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
The Room Three
Hidden mechanisms are unknown until inspected, then fixed
Portal leans a little harder on optimization, though the gap is small.
Portal
Pure puzzle-solving optimization.
The Room Three
Each puzzle box is a fully solvable mechanical system
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.