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
A twin-stick arcade shooter about surviving neon geometric enemy swarms for high score.
Colin McRae: Dirt 2 leans Execution (Pure Mechanics); Geometry Wars 3: Dimensions Evolved leans Execution (Pure Mechanics).
Geometry Wars 3: Dimensions Evolved leans a little harder on execution, though the gap is small.
Colin McRae: Dirt 2
precise rally driving and braking required
Geometry Wars 3: Dimensions Evolved
Twin-stick precision dodging and shooting under chaos.
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
Geometry Wars 3: Dimensions Evolved
No opponent modeling the player.
Geometry Wars 3: Dimensions Evolved leans a little harder on variance, though the gap is small.
Colin McRae: Dirt 2
weather and surface conditions vary
Geometry Wars 3: Dimensions Evolved
Enemy spawn patterns have randomized elements.
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
Geometry Wars 3: Dimensions Evolved
Scoring routes are learnable but execution dominates.
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.