head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is variance, and it is a single point.

Execution · Competitive PvP
Blockbuster 2009 sequel famous for killstreak chains and frantic multiplayer.

Execution · Competitive PvP
An acrobatic online shooter about movement-heavy gunplay against humans.
Call of Duty: Modern Warfare 2 leans Execution (Competitive PvP); GunZ 2: The Second Duel leans Execution (Competitive PvP).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty: Modern Warfare 2
Fast time-to-kill rewards raw aim and reflex
GunZ 2: The Second Duel
Acrobatic movement and aim are the core skill ceiling
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty: Modern Warfare 2
Outguessing human rotations and flanks
GunZ 2: The Second Duel
Against humans, predicting movement and fakes matters
Call of Duty: Modern Warfare 2 leans a little harder on variance, though the gap is small.
Call of Duty: Modern Warfare 2
Spawn flips and killstreak randomness
GunZ 2: The Second Duel
Minor weapon spread, mostly deterministic
Call of Duty: Modern Warfare 2 leans a little harder on optimization, though the gap is small.
Call of Duty: Modern Warfare 2
Killstreak economy, loadout and map knowledge
GunZ 2: The Second Duel
Class and loadout choices support but skill leads
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.