head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Execution · Practiced Mastery
Precise rally car control over stages that reward memorisation and tuning.

Execution · Practiced Mastery
Punishing platforming execution over learnable boss orders and part builds.
Dirt 3 leans Execution (Practiced Mastery); Mega Man X6 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.
Dirt 3
Car control on loose surfaces is a high physical ceiling
Mega Man X6
Cruel platforming and boss windows demand frame-tight inputs
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Dirt 3
Racing the clock or scripted AI, nobody adapts
Mega Man X6
Bosses are fixed pattern sets
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Dirt 3
Surface conditions and minor physics noise per run
Mega Man X6
The Nightmare System shuffles level hazards between runs
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Dirt 3
Stage knowledge and setup tuning reward study
Mega Man X6
Weapon orders, armor parts and route knowledge are essential
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.