head to head
Neither is simply harder - they are hard in different places. Hero's Quest: So You Want to Be a Hero demands more variance; Portal demands more execution.

Optimization · Pure Optimization
A class-based adventure-RPG hybrid about solving puzzles as a chosen hero archetype.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Hero's Quest: So You Want to Be a Hero leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Hero's Quest: So You Want to Be a Hero
minimal action, some timed puzzle sequences
Portal
Portal placement timing modest.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Hero's Quest: So You Want to Be a Hero
scripted monster encounters, no adaptation
Portal
No adversary modeling player.
Hero's Quest: So You Want to Be a Hero leans clearly harder on variance.
Hero's Quest: So You Want to Be a Hero
random encounters and skill-check rolls
Portal
Deterministic chambers; no randomness.
Portal leans clearly harder on optimization.
Hero's Quest: So You Want to Be a Hero
class-based build and puzzle-solving depth
Portal
Pure puzzle-solving optimization.
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.