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 · Practiced Mastery
Precise rally car control over stages that reward memorisation and tuning.

Execution · Pure Mechanics
A rally sim testing relentless car control plus stage memorisation and setup.
Dirt 3 leans Execution (Practiced Mastery); WRC 10 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.
Dirt 3
Car control on loose surfaces is a high physical ceiling
WRC 10
Rally car control on loose surfaces is relentless precision
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Dirt 3
Racing the clock or scripted AI, nobody adapts
WRC 10
Racing the clock, not a mind
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Dirt 3
Surface conditions and minor physics noise per run
WRC 10
Weather and surface conditions add modest unpredictability
Dirt 3 leans a little harder on optimization, though the gap is small.
Dirt 3
Stage knowledge and setup tuning reward study
WRC 10
Setup tuning and memorising stage notes 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.