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

Optimization · Pure Optimization
The archetypal idle game where optimal purchase order is the entire skill.

Optimization · Pure Optimization
A perfect-information tactics puzzle solved one turn at a time.
Cookie Clicker leans Optimization (Pure Optimization); Into the Breach leans Optimization (Pure Optimization).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Cookie Clicker
Clicking is optional past the early game
Into the Breach
No mechanical inputs
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Cookie Clicker
No opponent
Into the Breach
Enemy moves telegraphed fully each turn
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Cookie Clicker
Golden cookie timing randomness
Into the Breach
Light spawn and squad randomness
Into the Breach leans a little harder on optimization, though the gap is small.
Cookie Clicker
Purchase order and ascension math are the game
Into the Breach
Pure puzzle - perfect-information chess each turn
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.