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 · Practiced Mastery
Toy-car arcade racer about drift-charging boost on loop-the-loop tracks.
F-Zero X leans Execution (Pure Mechanics); Hot Wheels Unleashed leans Execution (Practiced Mastery).
F-Zero X leans a little harder on execution, though the gap is small.
F-Zero X
Sixty-frame control of thirty machines at top speed
Hot Wheels Unleashed
Drift-boost management on twisting plastic tracks
Hot Wheels Unleashed leans a little harder on reads, though the gap is small.
F-Zero X
Rival AI is non-adaptive
Hot Wheels Unleashed
Online races add light human jockeying
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
F-Zero X
X Cup random tracks are a minor mode
Hot Wheels Unleashed
Car unboxing randomness outside races
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
F-Zero X
Boost-health tradeoffs and shortcuts reward routing
Hot Wheels Unleashed
Car tiers, upgrades, and racing lines
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.