head to head
Neither is simply harder - they are hard in different places. Pokémon Pearl Version demands more variance; Portal 2 demands more execution.

Optimization · Pure Optimization
Type-matchup math and team construction across a scripted Sinnoh campaign.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.
Pokémon Pearl Version leans Optimization (Pure Optimization); Portal 2 leans Optimization (Pure Optimization).
Portal 2 leans clearly harder on execution.
Pokémon Pearl Version
Menu-driven battles need no dexterity
Portal 2
Portal placement requires some precision but timing is lenient.
Pokémon Pearl Version leans a little harder on reads, though the gap is small.
Pokémon Pearl Version
Gym leaders are scripted; online battles are optional
Portal 2
No opponent; puzzles are static.
Pokémon Pearl Version leans clearly harder on variance.
Pokémon Pearl Version
Encounter tables and battle rolls are mappable RNG
Portal 2
Puzzles are deterministic with no randomness.
Portal 2 leans clearly harder on optimization.
Pokémon Pearl Version
Team building and type matchups are the solvable core
Portal 2
Solving the puzzle's logic IS the entire game.
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.