head to head
Neither is simply harder - they are hard in different places. Crash Team Racing Nitro-Fueled demands more execution; Mario Kart 8 demands more variance.

Execution · Practiced Mastery
A kart racer demanding precise boost-chain execution and route optimisation over item luck.

Execution · Twitch Chaos
A kart racer where controlled chaos from random items tempers otherwise precise driving skill.
Crash Team Racing Nitro-Fueled leans Execution (Practiced Mastery); Mario Kart 8 leans Execution (Twitch Chaos).
Crash Team Racing Nitro-Fueled leans clearly harder on execution.
Crash Team Racing Nitro-Fueled
Boost-chain execution and power-slide timing are the lead skill
Mario Kart 8
precise drifting and item timing matter
Crash Team Racing Nitro-Fueled leans a little harder on reads, though the gap is small.
Crash Team Racing Nitro-Fueled
Human multiplayer has light item-use anticipation
Mario Kart 8
minimal, mostly reacting not predicting
Mario Kart 8 leans clearly harder on variance.
Crash Team Racing Nitro-Fueled
Item boxes and battle pickups introduce real outcome randomness
Mario Kart 8
item boxes are heavily randomized
Crash Team Racing Nitro-Fueled leans a little harder on optimization, though the gap is small.
Crash Team Racing Nitro-Fueled
Track-specific boost chains and shortcut routes are fully memorisable
Mario Kart 8
track lines and item strategy solvable
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.