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

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

Execution · Pure Mechanics
Pure point-and-shoot accuracy against memorisable scripted spawn patterns.
Colin McRae: Dirt 2 leans Execution (Pure Mechanics); Ghost Squad 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
Ghost Squad
Light-gun accuracy under time pressure 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
Ghost Squad
Terrorist spawns are scripted pop-up targets
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
Ghost Squad
Branching routes hide content until explored
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
Ghost Squad
Memorising spawn patterns per route raises scores
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.