head to head
Hardware: Rivals asks more than Dirt 5, and the gap is reads.

Execution · Pure Mechanics
Arcade car control across loose surfaces, weather and door-to-door packs.

Execution · Competitive PvP
Vehicular arena duels of handling and aim against human drivers.
Dirt 5 leans Execution (Pure Mechanics); Hardware: Rivals leans Execution (Competitive PvP).
Dirt 5 leans a little harder on execution, though the gap is small.
Dirt 5
Sliding off-road cars on mixed surfaces is the whole test
Hardware: Rivals
Vehicle handling and turret aim decide most duels
Hardware: Rivals leans clearly harder on reads.
Dirt 5
Pack racing adds light wheel-to-wheel jockeying
Hardware: Rivals
Human opponents' arena rotations reward some prediction
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
Hardware: Rivals
Pickup spawns add mild positional randomness
Dirt 5 leans a little harder on optimization, though the gap is small.
Dirt 5
Car class knowledge and line choice reward study
Hardware: Rivals
Weapon-pickup control and map knowledge underpin wins
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.