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
Bleak Ellison adaptation where five tortured souls face a sadistic AI.

Optimization · Systems & Chaos
A zany LucasArts adventure where a tabloid reporter foils aliens dumbing down humanity with a 60-Hz hum.
I Have No Mouth, and I Must Scream leans Optimization (Pure Optimization); Zak McKracken and the Alien Mindbenders leans Optimization (Systems & Chaos).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
I Have No Mouth, and I Must Scream
Pure point-and-click, no dexterity
Zak McKracken and the Alien Mindbenders
Verb-and-click interface; nothing physical.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
I Have No Mouth, and I Must Scream
AM is scripted despite the menace
Zak McKracken and the Alien Mindbenders
Dumb aliens run on rails; no adaptation anywhere.
Zak McKracken and the Alien Mindbenders leans a little harder on variance, though the gap is small.
I Have No Mouth, and I Must Scream
Obscure solutions hidden until discovered
Zak McKracken and the Alien Mindbenders
Globe-trotting item requirements are obscure on first play.
I Have No Mouth, and I Must Scream leans a little harder on optimization, though the gap is small.
I Have No Mouth, and I Must Scream
Puzzle chains and ethical-path knowledge
Zak McKracken and the Alien Mindbenders
Multi-character inventory chains form one big solvable puzzle.
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.
full breakdown
I Have No Mouth, and I Must Scream →
full breakdown
Zak McKracken and the Alien Mindbenders →