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
Arcade car control across loose surfaces, weather and door-to-door packs.

Execution · Practiced Mastery
An open-world arcade racer across Australia where car control and tuning carry every event.
Dirt 5 leans Execution (Pure Mechanics); Forza Horizon 3 leans Execution (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Dirt 5
Sliding off-road cars on mixed surfaces is the whole test
Forza Horizon 3
Car control and racing lines at speed
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Dirt 5
Pack racing adds light wheel-to-wheel jockeying
Forza Horizon 3
Drivatars mimic but don't truly adapt
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Dirt 5
Dynamic weather shifts grip unpredictably
Forza Horizon 3
Minor traffic and event variation
Forza Horizon 3 leans a little harder on optimization, though the gap is small.
Dirt 5
Car class knowledge and line choice reward study
Forza Horizon 3
Tuning, car choice, and route knowledge
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.