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

Execution · Pure Mechanics
The 70s-cinema getaway driving game with famously demanding physics.
Colin McRae: Dirt 2 leans Execution (Pure Mechanics); Driver leans Execution (Pure Mechanics).
Colin McRae: Dirt 2 leans a little harder on execution, though the gap is small.
Colin McRae: Dirt 2
precise rally driving and braking required
Driver
Handbrake control and pursuit driving by feel
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
Driver
Police AI is mappable
Colin McRae: Dirt 2 leans a little harder on variance, though the gap is small.
Colin McRae: Dirt 2
weather and surface conditions vary
Driver
Traffic adds mild unpredictability
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Colin McRae: Dirt 2
car tuning and racing lines solvable
Driver
City routes and mission tactics learnable
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.