head to head
Hitman asks more than Portal 2, and the gap is variance.

Optimization · Pure Optimization
A stealth puzzle game where meticulously planning the perfect assassination route is the whole point.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.
Hitman leans Optimization (Pure Optimization); Portal 2 leans Optimization (Pure Optimization).
Portal 2 leans a little harder on execution, though the gap is small.
Hitman
minimal twitch skill, stealth-focused
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.
Hitman
guard patrols scripted, no adaptation
Portal 2
No opponent; puzzles are static.
Hitman leans clearly harder on variance.
Hitman
some random guard behavior variance
Portal 2
Puzzles are deterministic with no randomness.
Portal 2 leans a little harder on optimization, though the gap is small.
Hitman
planning routes and disguises is fully 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.