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
Vehicular mayhem testing car handling plus knowing when wrecking beats racing.

Execution · Practiced Mastery
Open-world driving that tests car control with a tuning layer underneath.
Carmageddon II: Carpocalypse Now leans Execution (Practiced Mastery); Forza Horizon leans Execution (Practiced Mastery).
Forza Horizon leans a little harder on execution, though the gap is small.
Carmageddon II: Carpocalypse Now
Perfect car control trivialises wrecking AI opponents and surviving
Forza Horizon
Driving skill with assists off carries every event
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Carmageddon II: Carpocalypse Now
AI drivers follow set behaviours, never modelling the player
Forza Horizon
AI drivatars follow patterns; casual online adds little
Carmageddon II: Carpocalypse Now leans a little harder on variance, though the gap is small.
Carmageddon II: Carpocalypse Now
Pickup spawns and physics chaos add modest run-to-run noise
Forza Horizon
The open world is fixed and fully discoverable
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Carmageddon II: Carpocalypse Now
Choosing wreck-versus-race strategy and upgrade economy is solvable
Forza Horizon
Car tuning and racing lines reward systematic 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.