head to head
Neither is simply harder - they are hard in different places. Mario Kart 64 demands more reads; The Binding of Isaac: Repentance demands more optimization.

Execution · Twitch Chaos
N64 couch classic where blue shells and shortcuts decide friendships.

Execution · Twitch Chaos
Dodging bullets while leveraging encyclopedic item knowledge against heavy run RNG.
Mario Kart 64 leans Execution (Twitch Chaos); The Binding of Isaac: Repentance leans Execution (Twitch Chaos).
The Binding of Isaac: Repentance leans a little harder on execution, though the gap is small.
Mario Kart 64
Mini-turbo snaking and shortcut execution
The Binding of Isaac: Repentance
Dodging dense bullet patterns while aiming is constant pressure
Mario Kart 64 leans clearly harder on reads.
Mario Kart 64
Couch rivals bait shells and fakes
The Binding of Isaac: Repentance
Enemies are random or scripted, never modelling you
The Binding of Isaac: Repentance leans clearly harder on variance.
Mario Kart 64
Item draws swing every race
The Binding of Isaac: Repentance
Item pools and room rolls reshape every run
The Binding of Isaac: Repentance leans clearly harder on optimization.
Mario Kart 64
Shortcut and line knowledge is fully mapped
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.