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.

Variance · Light / Casual
A short, unsettling visual novel about intrusive thoughts with no skill test.
Firewatch leans Optimization (Light / Casual); Milk Inside a Bag of Milk Inside a Bag of Milk leans Variance (Light / Casual).
Firewatch leans a little harder on execution, though the gap is small.
Firewatch
Walking and radio dialogue only.
Milk Inside a Bag of Milk Inside a Bag of Milk
no physical skill demand at all
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.
Milk Inside a Bag of Milk Inside a Bag of Milk
no opponent of any kind
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.
Milk Inside a Bag of Milk Inside a Bag of Milk
branching text has minor unpredictability
Firewatch leans a little harder on optimization, though the gap is small.
Firewatch
Few systems to optimize.
Milk Inside a Bag of Milk Inside a Bag of Milk
barely any systems to solve
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.