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

Optimization · Pure Optimization
Hunting each level's optimal slingshot solution under mild physics noise.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.
Angry Birds Star Wars leans Optimization (Pure Optimization); Portal 2 leans Optimization (Pure Optimization).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Angry Birds Star Wars
Slingshot aim needs only mild touch precision
Portal 2
Portal placement requires some precision but timing is lenient.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Angry Birds Star Wars
Pigs sit motionless awaiting demolition
Portal 2
No opponent; puzzles are static.
Angry Birds Star Wars leans clearly harder on variance.
Angry Birds Star Wars
Physics tumbles add slight outcome noise per shot
Portal 2
Puzzles are deterministic with no randomness.
Portal 2 leans clearly harder on optimization.
Angry Birds Star Wars
Finding each level's three-star shot solution is the game
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.