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 LucasArts sci-fi adventure where astronauts stranded on an alien world puzzle out its dead civilization.

Optimization · Systems & Chaos
A zany LucasArts adventure where a tabloid reporter foils aliens dumbing down humanity with a 60-Hz hum.
The Dig 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.
The Dig
Point-and-click; no reflex demands.
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.
The Dig
Alien world is static; companions follow scripts.
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.
The Dig
Alien machinery's purpose is hidden until experimented with.
Zak McKracken and the Alien Mindbenders
Globe-trotting item requirements are obscure on first play.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
The Dig
Machine puzzles have single fixed solutions to deduce.
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.