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

Execution · Pure Mechanics
Committed rally driving where memorised stages meet precise throttle-and-slide control.

Execution · Practiced Mastery
Precise rally car control over stages that reward memorisation and tuning.
Colin McRae Rally 04 leans Execution (Pure Mechanics); Dirt 3 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.
Colin McRae Rally 04
Millisecond car control on loose surfaces is the whole test
Dirt 3
Car control on loose surfaces is a high physical ceiling
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Colin McRae Rally 04
Solo against the stage clock
Dirt 3
Racing the clock or scripted AI, nobody adapts
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Colin McRae Rally 04
Damage and surface conditions add minor unknowns
Dirt 3
Surface conditions and minor physics noise per run
Dirt 3 leans a little harder on optimization, though the gap is small.
Colin McRae Rally 04
Setup tuning and stage memorisation compound lap time
Dirt 3
Stage knowledge and setup tuning reward 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.