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

Optimization · Pure Optimization
Team-building optimisation against fixed trainers with mapped RNG.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Pokémon Ruby Version leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Pokémon Ruby Version
Turn selection requires no dexterity
Portal
Portal placement timing modest.
Pokémon Ruby Version leans a little harder on reads, though the gap is small.
Pokémon Ruby Version
Scripted trainers never adapt to your strategy
Portal
No adversary modeling player.
Pokémon Ruby Version leans clearly harder on variance.
Pokémon Ruby Version
Encounter, catch and crit rolls are quickly mapped
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 Ruby Version
Abilities and natures deepen an already solvable type system
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.