head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is variance, and it is a single point.

Optimization · Systems & Chaos
A noir detective adventure starring Discworld's first private investigator on a case that turns lycanthropic.

Optimization · Pure Optimization
Bleak Ellison adaptation where five tortured souls face a sadistic AI.
Discworld Noir leans Optimization (Systems & Chaos); I Have No Mouth, and I Must Scream 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.
Discworld Noir
Click-based sleuthing; nothing physical.
I Have No Mouth, and I Must Scream
Pure point-and-click, no dexterity
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Discworld Noir
Suspects recite fixed noir scripts.
I Have No Mouth, and I Must Scream
AM is scripted despite the menace
Discworld Noir leans a little harder on variance, though the gap is small.
Discworld Noir
Clue-notebook mystery hides connections until found.
I Have No Mouth, and I Must Scream
Obscure solutions hidden until discovered
I Have No Mouth, and I Must Scream leans a little harder on optimization, though the gap is small.
Discworld Noir
Cross-referencing clues converges to one fixed solution.
I Have No Mouth, and I Must Scream
Puzzle chains and ethical-path knowledge
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.