head to head
Neither is simply harder - they are hard in different places. Freelancer demands more variance; Portal 2 demands more optimization.

Optimization · Pure Optimization
A space sim where trade-route economics and ship progression matter as much as the accessible dogfighting.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.
Freelancer leans Optimization (Pure Optimization); Portal 2 leans Optimization (Pure Optimization).
Freelancer leans a little harder on execution, though the gap is small.
Freelancer
Mouse-flight dogfighting with modest ceiling
Portal 2
Portal placement requires some precision but timing is lenient.
Freelancer leans a little harder on reads, though the gap is small.
Freelancer
Pirate AI never adapts
Portal 2
No opponent; puzzles are static.
Freelancer leans clearly harder on variance.
Freelancer
Random encounters along trade lanes
Portal 2
Puzzles are deterministic with no randomness.
Portal 2 leans clearly harder on optimization.
Freelancer
Trade routes, ship upgrades, and faction standing are solvable
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.