head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Optimization · Pure Optimization
Bite-sized item-combination puzzles wrapped in comedy occult cases.

Optimization · Pure Optimization
A LucasArts sci-fi adventure where astronauts stranded on an alien world puzzle out its dead civilization.
The Darkside Detective leans Optimization (Pure Optimization); The Dig 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.
The Darkside Detective
Pointing and clicking has no physical bar
The Dig
Point-and-click; no reflex demands.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
The Darkside Detective
Cases are authored scripts, not adapting minds
The Dig
Alien world is static; companions follow scripts.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
The Darkside Detective
Solutions are hidden information until items are found
The Dig
Alien machinery's purpose is hidden until experimented with.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
The Darkside Detective
Item-combination puzzles each have one fixed answer
The Dig
Machine puzzles have single fixed solutions to deduce.
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.