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

Execution · Practiced Mastery
A serious F1 simulation testing precise car control and setup optimization.

Execution · Practiced Mastery
Simulation driving precision underpinned by setup tuning and race strategy.
Grand Prix 4 leans Execution (Practiced Mastery); Project CARS leans Execution (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Prix 4
Precise braking, throttle and racing-line control define lap times
Project CARS
Braking points and wheel control at the sim limit
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Prix 4
AI drivers follow scripted lines, not adapting to you
Project CARS
Online racecraft against humans adds light positional prediction
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Prix 4
Weather and grip add some unpredictability per race
Project CARS
Dynamic weather injects some session randomness
Grand Prix 4 leans a little harder on optimization, though the gap is small.
Grand Prix 4
Setup tuning and optimal lines are a deep solvable layer
Project CARS
Setup tuning and pit strategy reward deep study
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.