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

Optimization · Pure Optimization
A dark psychological point-and-click adventure driven by fixed puzzles and a disturbing story.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Fran Bow leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Fran Bow
Point-and-click inputs only
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.
Fran Bow
No opponents
Portal
No adversary modeling player.
Fran Bow leans clearly harder on variance.
Fran Bow
Hidden story layers until discovered
Portal
Deterministic chambers; no randomness.
Portal leans clearly harder on optimization.
Fran Bow
Fixed puzzle solutions; fully solvable
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.