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

Optimization · Light / Casual
A first-person mystery about a fire lookout in a Wyoming forest.

Execution · Light / Casual
Wordless watercolor platformer about grief, designed never to punish you.
Firewatch leans Optimization (Light / Casual); Gris leans Execution (Light / Casual).
Gris leans a little harder on execution, though the gap is small.
Firewatch
Walking and radio dialogue only.
Gris
Gentle platforming with no fail state
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Firewatch
No adaptive opposition.
Gris
No opposition at all
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Firewatch
Minor environmental discoveries.
Gris
Linear and fully authored
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Firewatch
Few systems to optimize.
Gris
Light environmental puzzles with obvious solutions
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.