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
A rally racer where mastering precise car control against tricky terrain is everything.

Execution · Pure Mechanics
Committed rally driving where memorised stages meet precise throttle-and-slide control.
Colin McRae: Dirt 2 leans Execution (Pure Mechanics); Colin McRae Rally 04 leans Execution (Pure Mechanics).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Colin McRae: Dirt 2
precise rally driving and braking required
Colin McRae Rally 04
Millisecond car control on loose surfaces is the whole test
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Colin McRae: Dirt 2
no adaptive opponents, mostly time trials
Colin McRae Rally 04
Solo against the stage clock
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Colin McRae: Dirt 2
weather and surface conditions vary
Colin McRae Rally 04
Damage and surface conditions add minor unknowns
Colin McRae Rally 04 leans a little harder on optimization, though the gap is small.
Colin McRae: Dirt 2
car tuning and racing lines solvable
Colin McRae Rally 04
Setup tuning and stage memorisation compound lap time
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.