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

Optimization · Pure Optimization
Open-world Pokémon where you tackle gyms and titans in any order.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Pokémon Scarlet leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Pokémon Scarlet
Open-world traversal, battles stay menu-based
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.
Pokémon Scarlet
NPC trainers never adapt
Portal
No adversary modeling player.
Pokémon Scarlet leans clearly harder on variance.
Pokémon Scarlet
Open-world spawns and tera raids
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.
Pokémon Scarlet
Terastallize typing adds a planning layer
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.