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

Optimization · Pure Optimization
Roguelite about raiding dungeons by night and pricing the loot in your shop by day.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.
Moonlighter leans Optimization (Pure Optimization); Portal 2 leans Optimization (Pure Optimization).
Moonlighter leans a little harder on execution, though the gap is small.
Moonlighter
Dodge-heavy dungeon combat
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.
Moonlighter
Enemies are scripted patterns
Portal 2
No opponent; puzzles are static.
Moonlighter leans clearly harder on variance.
Moonlighter
Random dungeon layouts and loot rolls
Portal 2
Puzzles are deterministic with no randomness.
Portal 2 leans clearly harder on optimization.
Moonlighter
Price discovery and shop economy are the real 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.