head to head
Neither is simply harder - they are hard in different places. LittleBigPlanet Karting demands more reads; Mario Kart 8 demands more variance.

Execution · Twitch Chaos
Item-luck kart racing with a creation suite bolted on.

Execution · Twitch Chaos
A kart racer where controlled chaos from random items tempers otherwise precise driving skill.
LittleBigPlanet Karting leans Execution (Twitch Chaos); Mario Kart 8 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.
LittleBigPlanet Karting
Drifting and weapon timing decide most races
Mario Kart 8
precise drifting and item timing matter
LittleBigPlanet Karting leans clearly harder on reads.
LittleBigPlanet Karting
Human racers add light prediction in item battles
Mario Kart 8
minimal, mostly reacting not predicting
Mario Kart 8 leans clearly harder on variance.
LittleBigPlanet Karting
Random item pickups swing positions constantly
Mario Kart 8
item boxes are heavily randomized
Mario Kart 8 leans clearly harder on optimization.
LittleBigPlanet Karting
Track lines and shortcut knowledge give a modest edge
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.