head to head
Neither is simply harder - they are hard in different places. Portal 2 demands more optimization; Super Mario RPG: Legend of the Seven Stars demands more variance.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.

Optimization · Pure Optimization
A charming turn-based RPG where timed button presses add light dexterity to simple optimization.
Portal 2 leans Optimization (Pure Optimization); Super Mario RPG: Legend of the Seven Stars 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.
Portal 2
Portal placement requires some precision but timing is lenient.
Super Mario RPG: Legend of the Seven Stars
Timed hits and blocks reward rhythm.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Portal 2
No opponent; puzzles are static.
Super Mario RPG: Legend of the Seven Stars
Bosses use fixed attack scripts.
Super Mario RPG: Legend of the Seven Stars leans clearly harder on variance.
Portal 2
Puzzles are deterministic with no randomness.
Super Mario RPG: Legend of the Seven Stars
Hidden chests and first-run boss surprises.
Portal 2 leans clearly harder on optimization.
Portal 2
Solving the puzzle's logic IS the entire game.
Super Mario RPG: Legend of the Seven Stars
Gear, timing knowledge, and stat routing solve fights.
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.