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

Optimization · Pure Optimization
A hidden-object adventure about searching scenes and solving fixed puzzles.

Optimization · Pure Optimization
A mechanical journey adventure solved by understanding the logic of its automaton-filled world.
Mystery Case Files: 13th Skull leans Optimization (Pure Optimization); Syberia 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.
Mystery Case Files: 13th Skull
Pointing and clicking, no twitch demand
Syberia
Walking and clicking; zero reflex demand
Mystery Case Files: 13th Skull leans a little harder on reads, though the gap is small.
Mystery Case Files: 13th Skull
No adaptive opponent, puzzles are fixed
Syberia
NPCs follow scripted dialogue trees with no adaptive modelling
Mystery Case Files: 13th Skull leans a little harder on variance, though the gap is small.
Mystery Case Files: 13th Skull
Hidden-object locations unknown until searched
Syberia
Linear journey with virtually no hidden-information surprises
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Mystery Case Files: 13th Skull
Solving puzzles and finding objects is the whole loop
Syberia
Mechanical clockwork puzzles require mapping part relationships
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.