head to head
Orcs Must Die! Unchained asks more than Grand Theft Auto V, and the gap is reads.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.

Optimization · Practiced Mastery
Trap-maze economics against human attackers who adapt their pushes.
Grand Theft Auto V leans Execution (Practiced Mastery); Orcs Must Die! Unchained leans Optimization (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Orcs Must Die! Unchained
Third-person combat matters but traps do the killing
Orcs Must Die! Unchained leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Orcs Must Die! Unchained
PvP sieges reward predicting enemy pushes and trap placement
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Theft Auto V
Some mission and lobby randomness.
Orcs Must Die! Unchained
Card draws and minion waves add mild noise
Orcs Must Die! Unchained leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
Orcs Must Die! Unchained
Trap economy and maze layout theory decide fortresses
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.