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 choice-driven comedy adventure with almost no skill test at all.
Firewatch leans Optimization (Light / Casual); Tales from the Borderlands 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.
Tales from the Borderlands
Occasional QTEs are the only physical demand
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.
Tales from the Borderlands
No opponent of any kind
Tales from the Borderlands leans a little harder on variance, though the gap is small.
Firewatch
Minor environmental discoveries.
Tales from the Borderlands
Story branches are unknown until chosen
Firewatch leans a little harder on optimization, though the gap is small.
Firewatch
Few systems to optimize.
Tales from the Borderlands
Choices barely change outcomes; nothing 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.