head to head
Neither is simply harder - they are hard in different places. Dead Nation: Apocalypse Edition demands more execution; Grand Theft Auto V demands more reads.

Execution · Practiced Mastery
A twin-stick zombie shooter testing kiting discipline and upgrade routing.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.
Dead Nation: Apocalypse Edition leans Execution (Practiced Mastery); Grand Theft Auto V leans Execution (Practiced Mastery).
Dead Nation: Apocalypse Edition leans clearly harder on execution.
Dead Nation: Apocalypse Edition
Aiming and kiting dense zombie swarms is the core test
Grand Theft Auto V
Driving and shooting demand decent inputs.
Grand Theft Auto V leans clearly harder on reads.
Dead Nation: Apocalypse Edition
Zombies follow simple scripted pursuit
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Dead Nation: Apocalypse Edition
Spawns vary slightly between runs
Grand Theft Auto V
Some mission and lobby randomness.
Dead Nation: Apocalypse Edition leans a little harder on optimization, though the gap is small.
Dead Nation: Apocalypse Edition
Weapon upgrades and crowd-routing reward planning
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.