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
A story-driven skateboarding game still won by trick execution.

Execution · Pure Mechanics
Grinding deterministic tracks for the perfect line and the flawless run.
Tony Hawk's Underground leans Execution (Practiced Mastery); TrackMania 2: Stadium leans Execution (Pure Mechanics).
TrackMania 2: Stadium leans a little harder on execution, though the gap is small.
Tony Hawk's Underground
Combos plus off-board tricks keep the input ceiling high
TrackMania 2: Stadium
Perfect inputs ARE the game - hundredths decide leaderboards
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Tony Hawk's Underground
Story missions are scripted, not adaptive
TrackMania 2: Stadium
Ghost racing - opponents never interact with your run
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Tony Hawk's Underground
Fixed levels and mission scripts
TrackMania 2: Stadium
Fully deterministic physics, identical track every attempt
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Tony Hawk's Underground
Mission and score-line routing remain solvable
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.