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

Optimization · Pure Optimization
Solvable team-building progression through an all-new fixed roster.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Pokémon White Version leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Pokémon White Version
Menu battles need no dexterity
Portal
Portal placement timing modest.
Pokémon White Version leans a little harder on reads, though the gap is small.
Pokémon White Version
Campaign trainers are scripted; competitive play is separate
Portal
No adversary modeling player.
Pokémon White Version leans clearly harder on variance.
Pokémon White Version
All-new Pokémon are unknowns until the dex fills
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 White Version
Fresh type matchups still reduce to solvable team building
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.