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 · Practiced Mastery
A top-down co-op shooter testing aim against waves of mutants.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.
Dead Horde leans Execution (Practiced Mastery); Grand Theft Auto V leans Execution (Practiced Mastery).
Dead Horde leans a little harder on execution, though the gap is small.
Dead Horde
Top-down aiming against mutant swarms is core
Grand Theft Auto V
Driving and shooting demand decent inputs.
Grand Theft Auto V leans a little harder on reads, though the gap is small.
Dead Horde
Enemies are scripted hordes, nothing adapts
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Dead Horde leans a little harder on variance, though the gap is small.
Dead Horde
Spawn directions add some unpredictability
Grand Theft Auto V
Some mission and lobby randomness.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Dead Horde
Weapon choice and positioning plan survival
Grand Theft Auto V
Heists, money loops, builds learnable.
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.