head to head
Neither is simply harder - they are hard in different places. Enigmatis 3: The Shadow of Karkhala demands more variance; Portal 2 demands more optimization.

Optimization · Pure Optimization
A hidden-object detective adventure testing fixed-puzzle deduction.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.
Enigmatis 3: The Shadow of Karkhala leans Optimization (Pure Optimization); Portal 2 leans Optimization (Pure Optimization).
Portal 2 leans clearly harder on execution.
Enigmatis 3: The Shadow of Karkhala
Point-and-click needs no motor precision
Portal 2
Portal placement requires some precision but timing is lenient.
Enigmatis 3: The Shadow of Karkhala leans a little harder on reads, though the gap is small.
Enigmatis 3: The Shadow of Karkhala
Solo detective story; no adaptive opponent
Portal 2
No opponent; puzzles are static.
Enigmatis 3: The Shadow of Karkhala leans clearly harder on variance.
Enigmatis 3: The Shadow of Karkhala
Hidden objects but fixed per-scene solutions
Portal 2
Puzzles are deterministic with no randomness.
Portal 2 leans clearly harder on optimization.
Enigmatis 3: The Shadow of Karkhala
Solving fixed puzzles and clue routing is the loop
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.