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

Optimization · Pure Optimization
A physics puzzle game testing projectile angle and aim to demolish castles.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.
Crush the Castle leans Optimization (Pure Optimization); Portal 2 leans Optimization (Pure Optimization).
Crush the Castle leans a little harder on execution, though the gap is small.
Crush the Castle
Release timing of the trebuchet needs some 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.
Crush the Castle
Solo physics puzzle, no opponent to predict
Portal 2
No opponent; puzzles are static.
Crush the Castle leans clearly harder on variance.
Crush the Castle
Deterministic physics, minimal randomness
Portal 2
Puzzles are deterministic with no randomness.
Portal 2 leans clearly harder on optimization.
Crush the Castle
Finding optimal projectile angles to topple structures is 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.