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
Kart-racing control with item RNG swinging family-friendly races.

Execution · Pure Mechanics
Demolition derby racer with destructible PvP chaos.
F1 Race Stars leans Execution (Twitch Chaos); Wreckfest leans Execution (Pure Mechanics).
Wreckfest leans a little harder on execution, though the gap is small.
F1 Race Stars
Kart handling and boost timing decide clean laps
Wreckfest
Demolition driving, ramming angles
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
F1 Race Stars
Human racers feint and time item attacks in multiplayer
Wreckfest
Online derby PvP rewards ramming reads
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
F1 Race Stars
Item rolls swing positions like any kart racer
Wreckfest
Crash physics chaos
Wreckfest leans a little harder on optimization, though the gap is small.
F1 Race Stars
Track shortcuts and KERS timing are learnable edges
Wreckfest
Car upgrades and durability tuning
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.