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 · Competitive PvP
Vehicular arena duels of handling and aim against human drivers.

Execution · Pure Mechanics
Tests precise steering on cramped miniature tracks where one slip means falling off the table.
Hardware: Rivals leans Execution (Competitive PvP); Micro Machines leans Execution (Pure Mechanics).
Micro Machines leans a little harder on execution, though the gap is small.
Hardware: Rivals
Vehicle handling and turret aim decide most duels
Micro Machines
Tiny cars on twisty tabletop tracks demand constant precise steering
Hardware: Rivals leans a little harder on reads, though the gap is small.
Hardware: Rivals
Human opponents' arena rotations reward some prediction
Micro Machines
Local multiplayer screen-edge duels reward predicting rivals' lines
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Hardware: Rivals
Pickup spawns add mild positional randomness
Micro Machines
Tracks are fixed; little randomness beyond AI bumping
Micro Machines leans a little harder on optimization, though the gap is small.
Hardware: Rivals
Weapon-pickup control and map knowledge underpin wins
Micro Machines
Learning each track's racing line and shortcuts pays off
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.