head to head
Neither is simply harder - they are hard in different places. Football Club Simulator - FCS demands more variance; Portal demands more execution.

Optimization · Pure Optimization
A football management sim testing tactics, squad building and club economics.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Football Club Simulator - FCS leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Football Club Simulator - FCS
Real-time orders, but no twitch ceiling
Portal
Portal placement timing modest.
Football Club Simulator - FCS leans clearly harder on reads.
Football Club Simulator - FCS
Opponent managers offer light tactical prediction
Portal
No adversary modeling player.
Football Club Simulator - FCS leans clearly harder on variance.
Football Club Simulator - FCS
Match outcomes and player form carry randomness
Portal
Deterministic chambers; no randomness.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Football Club Simulator - FCS
Squad building, tactics and club finances decide success
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.