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 · Practiced Mastery
An encyclopedic driving simulator spanning 700 cars and decades of automotive history.

Execution · Practiced Mastery
Pure time-trial racing testing relentless execution of an ever-more-optimised line.
Gran Turismo 4 leans Execution (Practiced Mastery); TrackMania United Forever leans Execution (Practiced Mastery).
TrackMania United Forever leans a little harder on execution, though the gap is small.
Gran Turismo 4
Hundreds of cars all demand precise inputs
TrackMania United Forever
Frame-perfect lines over hundreds of restarts are everything
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Gran Turismo 4
Fixed-line AI offers no adaptive opposition
TrackMania United Forever
Time trials against ghosts - no one adapts to you
Gran Turismo 4 leans a little harder on variance, though the gap is small.
Gran Turismo 4
Deterministic outside slight tyre wear modelling
TrackMania United Forever
Deterministic physics with literally nothing hidden
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Gran Turismo 4
Event-by-event car and tune selection is deeply solvable
TrackMania United Forever
Finding the theoretical fastest line is the meta-game
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.