head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is reads, and it is a single point.

Execution · Practiced Mastery
Chaotic vehicular destruction testing driving control and map knowledge.

Execution · Practiced Mastery
Managing air meter and shortcut routes at speed on memorised tracks.
Carmageddon: Max Damage leans Execution (Practiced Mastery); Sonic Riders leans Execution (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Carmageddon: Max Damage
Vehicular mayhem rewards precise ramming and recovery driving
Sonic Riders
Air management, drift timing and shortcuts demand practiced hands
Sonic Riders leans a little harder on reads, though the gap is small.
Carmageddon: Max Damage
AI rivals follow routines, not your mind
Sonic Riders
Versus humans there is mild positional jockeying
Carmageddon: Max Damage leans a little harder on variance, though the gap is small.
Carmageddon: Max Damage
Physics chaos and pickup spawns scramble outcomes
Sonic Riders
Item and turbulence placement adds light randomness
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Carmageddon: Max Damage
Knowing maps, shortcuts and wreck-economy wins events
Sonic Riders
Gear choice and shortcut routes reward track 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.