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.

Variance · Light / Casual
A short, unsettling visual novel about intrusive thoughts with no skill test.

Variance · Light / Casual
A short horror visual novel seen through a man whose senses render the world as flesh.
Milk Inside a Bag of Milk Inside a Bag of Milk leans Variance (Light / Casual); The Song of Saya 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.
Milk Inside a Bag of Milk Inside a Bag of Milk
no physical skill demand at all
The Song of Saya
No dexterity component; pure reading
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Milk Inside a Bag of Milk Inside a Bag of Milk
no opponent of any kind
The Song of Saya
No opponent of any kind
The Song of Saya leans a little harder on variance, though the gap is small.
Milk Inside a Bag of Milk Inside a Bag of Milk
branching text has minor unpredictability
The Song of Saya
A few branch choices hide unseen endings
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Milk Inside a Bag of Milk Inside a Bag of Milk
barely any systems to solve
The Song of Saya
Minimal choice mapping across three endings
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.