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

Execution · Twitch Chaos
A kart racer where controlled chaos from random items tempers otherwise precise driving skill.

Execution · Twitch Chaos
Twin-stick roguelike where a crying child fights basement horrors with random unholy upgrades.
Mario Kart 8 leans Execution (Twitch Chaos); The Binding of Isaac leans Execution (Twitch Chaos).
The Binding of Isaac leans a little harder on execution, though the gap is small.
Mario Kart 8
precise drifting and item timing matter
The Binding of Isaac
Twin-stick dodging through bullet-dense rooms
Mario Kart 8 leans a little harder on reads, though the gap is small.
Mario Kart 8
minimal, mostly reacting not predicting
The Binding of Isaac
Enemies follow fixed or random patterns
The Binding of Isaac leans a little harder on variance, though the gap is small.
Mario Kart 8
item boxes are heavily randomized
The Binding of Isaac
Item and room RNG defines every run
The Binding of Isaac leans a little harder on optimization, though the gap is small.
Mario Kart 8
track lines and item strategy solvable
The Binding of Isaac
Item synergy knowledge converts luck 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.