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
Co-op FPS about four masked crooks holding out through scripted heist assaults.

Execution · Pure Mechanics
A twin-stick shooter testing aim and crowd control across zombie waves.
Payday: The Heist leans Execution (Practiced Mastery); Zombie Apocalypse leans Execution (Pure Mechanics).
Zombie Apocalypse leans a little harder on execution, though the gap is small.
Payday: The Heist
Holding off assault waves takes solid gunplay
Zombie Apocalypse
Dual-stick aiming and dodging carry the survival
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Payday: The Heist
Police waves are scripted spawns
Zombie Apocalypse
Zombies swarm without adapting to you
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Payday: The Heist
Drill failures and objective locations shuffle
Zombie Apocalypse
Spawn waves and hazard timing add chaos
Payday: The Heist leans a little harder on optimization, though the gap is small.
Payday: The Heist
Crew positioning and objective sequencing per heist
Zombie Apocalypse
Using environmental hazards and weapon choice efficiently
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.