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 · Pure Mechanics
The N64 entry whose boost-or-survive health gamble layers routing decisions onto raw speed control.

Execution · Pure Mechanics
Grinding deterministic tracks for the perfect line and the flawless run.
F-Zero X leans Execution (Pure Mechanics); TrackMania 2: Stadium leans Execution (Pure Mechanics).
TrackMania 2: Stadium leans a little harder on execution, though the gap is small.
F-Zero X
Sixty-frame control of thirty machines at top speed
TrackMania 2: Stadium
Perfect inputs ARE the game - hundredths decide leaderboards
F-Zero X leans a little harder on reads, though the gap is small.
F-Zero X
Rival AI is non-adaptive
TrackMania 2: Stadium
Ghost racing - opponents never interact with your run
F-Zero X leans a little harder on variance, though the gap is small.
F-Zero X
X Cup random tracks are a minor mode
TrackMania 2: Stadium
Fully deterministic physics, identical track every attempt
TrackMania 2: Stadium leans a little harder on optimization, though the gap is small.
F-Zero X
Boost-health tradeoffs and shortcuts reward routing
TrackMania 2: Stadium
Finding the optimal racing line is half the hunt
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.