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 · Light / Casual
A hidden-object game about spotting one hundred dogs in a scene.

Optimization · Light / Casual
A first-person mystery about a fire lookout in a Wyoming forest.
100 Hidden Dogs leans Optimization (Light / Casual); Firewatch leans Optimization (Light / Casual).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
100 Hidden Dogs
Clicking spotted dogs needs no precision
Firewatch
Walking and radio dialogue only.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
100 Hidden Dogs
Solo - no opponent to predict
Firewatch
No adaptive opposition.
100 Hidden Dogs leans a little harder on variance, though the gap is small.
100 Hidden Dogs
Dog locations hidden until you find them
Firewatch
Minor environmental discoveries.
100 Hidden Dogs leans a little harder on optimization, though the gap is small.
100 Hidden Dogs
Systematic scanning of the scene finds them all
Firewatch
Few systems to optimize.
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.