head to head
Neither is simply harder - they are hard in different places. Left 4 Dead demands more reads; The Binding of Isaac: Repentance demands more variance.

Execution · Twitch Chaos
Co-op zombie shooter whose AI Director reshuffles every run to keep teams honest.

Execution · Twitch Chaos
Dodging bullets while leveraging encyclopedic item knowledge against heavy run RNG.
Left 4 Dead leans Execution (Twitch Chaos); The Binding of Isaac: Repentance leans Execution (Twitch Chaos).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Left 4 Dead
Headshots, melee shoves, and special-infected reaction time
The Binding of Isaac: Repentance
Dodging dense bullet patterns while aiming is constant pressure
Left 4 Dead leans clearly harder on reads.
Left 4 Dead
Versus mode adds human ambush mindgames
The Binding of Isaac: Repentance
Enemies are random or scripted, never modelling you
The Binding of Isaac: Repentance leans clearly harder on variance.
Left 4 Dead
AI Director randomizes hordes, items, and specials
The Binding of Isaac: Repentance
Item pools and room rolls reshape every run
The Binding of Isaac: Repentance leans clearly harder on optimization.
Left 4 Dead
Team spacing, route choice, and resource discipline
The Binding of Isaac: Repentance
Knowing hundreds of item synergies converts RNG into wins
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.