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 · Pure Optimization
A notoriously difficult comedy adventure where Rincewind the inept wizard must rid Ankh-Morpork of a dragon.

Optimization · Pure Optimization
Bleak Ellison adaptation where five tortured souls face a sadistic AI.
Discworld leans Optimization (Pure Optimization); 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
Point-and-click; no manual ceiling.
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
Ankh-Morpork's citizens are scripted gag dispensers.
I Have No Mouth, and I Must Scream
AM is scripted despite the menace
Discworld leans a little harder on variance, though the gap is small.
Discworld
Infamously obscure puzzle logic blindsides every first-timer.
I Have No Mouth, and I Must Scream
Obscure solutions hidden until discovered
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Discworld
Byzantine item chains are brutal but fully solvable.
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.