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 first-person mystery about a fire lookout in a Wyoming forest.

Variance · Light / Casual
A short authored branching story; the test is choice, not skill.
Firewatch leans Optimization (Light / Casual); The Walking Dead: Michonne leans Variance (Light / Casual).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Firewatch
Walking and radio dialogue only.
The Walking Dead: Michonne
Forgiving QTE prompts, no real skill ceiling
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.
The Walking Dead: Michonne
Authored characters, nothing adapts
The Walking Dead: Michonne leans a little harder on variance, though the gap is small.
Firewatch
Minor environmental discoveries.
The Walking Dead: Michonne
Branch outcomes are hidden only on first viewing
Firewatch leans a little harder on optimization, though the gap is small.
Firewatch
Few systems to optimize.
The Walking Dead: Michonne
Almost nothing to solve beyond watching choices play out
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.