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

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

Optimization · Pure Optimization
Evidence-gathering and deduction-board logic with no physical or adversarial layer.
The Darkside Detective leans Optimization (Pure Optimization); The Testament of Sherlock Holmes 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 Testament of Sherlock Holmes
Pointing and clicking through crime scenes
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 Testament of Sherlock Holmes
Suspects are written, not adapting
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 Testament of Sherlock Holmes
Clues are hidden information until uncovered
The Testament of Sherlock Holmes leans a little harder on optimization, though the gap is small.
The Darkside Detective
Item-combination puzzles each have one fixed answer
The Testament of Sherlock Holmes
The deduction board is a solvable logic 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.